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A  PRACTICAL  TREATISE 


PREPARATION,  COMBINATION  AND 
APPLICATION 

OF 

CALCAREOUS  AND  HYDRAULIC 
LIMES  AND  CEMENTS, 

COMPILED  AND  ARRANGED  FROM  THE  BEST  AUTHORITIES,  AND 
FROM  THE  PRACTICAL  EXPERIENCE  OF  THE  COMPILER 
DURING  A  LONG  PROFESSIONAL  CAREER, 

»*o  ^VIIieH-KS  ALDf^D'MANY    '         ' '  "*  '  ' 

USEFUL   RECIPE^ '  -FOR  VARIOOS'  SCIENTIFIC, 
MERCANTILE  AND  pOMESTlC  :PUii:?,(^5ES. 


JAMES  G.  AUSTIN, 

ARCHITECT. 


NEW  YORK: 
JOHN  WILEY  &  SON, 
15,  ASTOR  PLACE. 


1871. 


OOA/S 


PEEFACE. 


The  following  pages  (which  make  but  little  pretensions  to 
originality)  are  presented  to  the  notice  of  the  Building  Pro- 
fession, as  a  concise  and  useful  work  upon  the  important  subject 
of  Limes  and  Cements,  and  with  a  view  to  attract  public 
attention  to  their  essential  properties,  analysis,  combination 
and  application,  as  described  in  a  rare,  but  highly  esteemed 
and  valued  work  (long  since  out  of  print)  by  Dr.  Brindley 
Higgins,  the  theories  and  experiments  therein  enunciated  and 
defined  having  been  practically  confirmed  by  the  compiler, 
during  a  long  professional  career,  and  also  as  embodying  the 
best  modern  experience  and  information  upon  the  subject, 
derived  from  high  authority  (which  is  duly  acknowledged) 
interspersed  with  practical  remarks  by  the  Author,  to  w^hich 
is  added  much  that  is  useful  to  the  engineer,  geologist,  and 
American  citizen,  and  now  humbly  and  respectfully  submitted 
to  the  patronage  of  an  enlightened  public. 

March,  1862. 


GENERAL  REMARKS. 


Cements  are  of  two  distinct  classes,  viz.,  Ca/ca?-eows(or those  which 
are  used  for  works  exposed  to  the  air;) and  Hydraulic^{ox  such  as  are 
used  under  water  ,*)they  are  also  further  distinguished  as  Hot  and  Cold. 
The  former  are  those  which  are  applied  by  the  aid  of  heat  or  fire,  and 
which  contain,  rosin,  resin,  bees-wax,  and  such  like  substances ;  and 
the  latter,  those  which  are  applied  through  the  medium  of  alcohol, 
water,  or  oil,  and  are  chiefly  composed  of  calcareous  and  other  earthy 
matters. 

Calcareous  Cement  or  mortar  is  a  most  important  auxilliary  in 
the  construction  of  every  description  of  brickwork,  and  masonry,  and 
is  universally  known  by  the  term  mortar." 

Hydraulic  Cements  are  those  whose  property  is  to  indurate  or 
to  harden  under  water,  and  are  consequently  indispensable  in  the 
construction  of  bridges,  docks,  quays,  and  other  marine  works. 

Plastic  Cements  are  such  as  are  more  particularly  applied  to  the 
stuccoing  or  incrustation  of  the  exterior  and  interior  surfaces  of  walls, 
&c.,  the  use  of  which  is  more  applicable  to  the  plasterer's  art. 

The  above  three  classes  or  divisions  will  be  separately  treated  and 
explained,  in  consecutive  order — ^but  before  entering  into  the  descrip- 
tion of  the  composition  of  either  of  them,  it  would  be  necessary  first 
to  consider  and  to  define  the  nature,  properties,  and  qualifications  of 
the  several  ingredients  of  which  ordinary  mortar  is  composed,  and  to 
describe  the  principal  varieties  in  use,  pointing  out  the  relative  use 
and  value  of  each,  and  then  to  describe  the  proportions  of  the  several 
ingredients,  and  afterwards  to  explain  the  mode  of  combining  and 
applying  them  to  building  purposes. 


COMPONENTS  OF  MORTAR. 


Lime. — Of  this  important  ingredient  there  are  numerous  varieties 
possessing  different  qualities  and  merit.  They  are  prepared  from  the 
following  minerals,  viz.  :  marble,  limestone  (of  which  there  are  seve- 
ral varieties),  chalk,  oyster  and  other  shells,  and  also  from  other  cal- 
careous or  carboniferous  stones,  which,  when  subjected  to  a  red  heat 
and  calcined,  will  dissolve  and  effervesce  with  acid ;  and  as  a  general 
rule  it  may  be  remarked  that  the  harder  the  stone  or  other  material 
is,  the  better  will  be  the  quality  of  the  lime,  and  that  which  dissolves 
the  quickest,  heats  the  most  in  slaldng,  and  falls  into  the  finest  pow- 
der, is  the  best. 

Lime  is  usually  found  in  connection  with  an  acid,  and  by  subjecting 
it  to  a  red  heat  the  acid  is  evolved,  leaving  the  lime  in  a  pure  state, 
■»vhich  is  then  termed  caustic  or  quick  lime,  and  is  then  fit  for  admix- 
ture with  the  other  ingredients  to  form  mortar  or  cement. 

Of  the  method  of  preparing  lime  from  the  crude  material,  it  will  be 
irrelevant  here  to  speak,  but  the  operation  will  be  found  amongst 
the  "addenda"  at  the  end  of  this  treatise. 

Lime  should  be  used  fresh  from  the  kiln,  or  otherwise  it  must  be  se- 
cured from  the  air,  in  close  casks  or  other  receptacles,  till  required  for 
use,  or  it  will  by  exposure  readily  absorb  the  carbonic  acid  gas  from 
the  atmosphere,  to  discharge  which  is  the  principal  object  of  burning 
or  calcining  it ;  and  lime,  when  once  it  is  slaked,  should  be  im- 
mediately used  or  it  would  become  effete  or  dead,  or  for  all  cementi- 
tious  purposes,  perfectly  useless. 

Limestones  lose  about  four-ninths  of  their  weight  in  burning,  though 
they  slirink  but  little,  but  when  properly  burnt  and  slaked  to  a 
powder,  they  acquire  nearly  double  their  former  bulk. 

Chalk  and  lime  stones  if  equally  fresh  and  well  burnt,  differ  but  little 
in  their  cementitious  properties,  but  as  slaked  lime  absorbs  carbonic 


COMPONENTS  OF  MORTAR. 


7 


gas  in  proportion  to  its  textui'e  (solidity),  so  it  yields  its  cementing 
properties  the  more  freely  by  exposure ;  therefore,  although  stone  and 
chalk  limes  be  equally  good  at  first,  yet  there  will  exist  a  great  diifer- 
ence,  subsequently ;  because  the  latter  becomes  more  readily  affected 
or  injured  by  the  atmosphere  than  the  former,  upon  which  fact,  the 
preference  for  stone  limes  has  been,  obtained. 

Dr.  Higgins  in  his  work  on  Calcareous  Cements"  &c.,  section  2, 
entitled  Experiments  and  Observations  on  Limestone  and  Lime," 
makes  the  following  observ^ations  (the  result  of  practical  experiments) 
upon  the  properties  of  limestones,  chalk  and  lime : — 

Observation.  1.  Limestone  or  chalk  heated  only  to  redness,  in  a 
covered  crucible,  or  a  perforated  one,  through  which  the  air  circulates 
freely,  loses  only  about  one-fourth  of  its  weight,  however  long  this 
heat  be  continued.  The  sort  of  lime  so  formed,  effervesces  considera- 
bly in  acid,  slakes  slowly  and  partially  to  a  gray  or  brown  powder, 
and  heats  but  little  in  slaking ;  by  heat  is  meant  that  degree  of  it 
which  the  bodies  themselves  (limestones,  &c.)  are  made  to  conceive 
equally  through  their  whole  mass  during  the  operation  of  burning. 

Obs.  2.  Limestone  or  chalk  exposed  to  a  heat  barely  sufficient  to 
melt  copper,  whether  in  a  perforated  crucible  or  otherwise,  loses  about 
one-third  of  its  weight  in  twelve  hours,  and  very  little  more  in  any 
longer  time.  This  lime  effervesces  but  slightly  in  acids,  heats  much 
sooner,  and  more  strongly  than  the  former  when  wetted,  and  slakes 
more  equally  and  to  a  whiter  powder.  In  a  variety  of  trials  this 
lime  equalled  the  best  specimens  prepared  in  common  lime-  kilns,  and 
the  amount  of  acidulous  gas  obtainable  from  each  by  a  stronger 
heat,  or  in  solution,  were  nearly  equal ;  they  slaked  in  like  periods, 
with  the  same  phenomena,  color,  and  condition  of  powder. 

Obs.  3.  The  lime  burned  in  perforated  crucibles,  or  in  the  naked 
fire,  is  whiter  than  that  burned  in  common  crucibles,  covered,  in 
which  latter  case  the  air  has  not  free  access  to  it,  although  the  loss 
of  weight  be  the  same  in  both ;  but  this  latter  kind  of  lime,  in  slak- 


8 


COMPONENTS  OF  MORTAR. 


ing,  affords  as  white  a  powder  as  any  other  which  has  lost  equally  of 
its  weight.  Whatever  portion  of  phlogiston  it  retains  to  produce  the 
dusky  color,  it  is  either  detached  in  slaking,  or  does  not  sensibly  affect 
the  lime  in  any  use  to  which  it  may  be  applied. 

Obs.  4.  When  dry  chalk  or  limestone  is  used  in  the  process  above 
described  for  making  lime  in  close  vessels,  and  for  examining  the 
matter  which  is  expelled  by  fire,  the  quantity  of  water  obtainable 
from  it  by  heat  is  so  inconsiderable  as  to  deserve  no  notice  in  the 
calculation  of  that  matter. 

Obs.  5.  Chalk  or  limestone  heated  gradually  in  close  vessels  loses 
very  little  acidulous  gas  until  it  begins  to  redden,  after  which  the 
elastic  fluid  issues  from  it  quicker  as  the  heat  increases,  and  so 
continues  until  the  vessel  attains  a  heat  sufficient  to  melt  steel. 

Obs.  6.  Forty-eight  ounces  of  chalk  yield  twenty-one  ounces  of 
elastic  fluid,  the  first  issues  of  which  are  turbid,  but  soon  become 
clear  without  loss  of  bulk,  by  the  condensation  of  the  aqueous  fluid ; 
the  remaining  portions  being  transparent  and  invisible,  one  thirty- 
sixth  part  of  this  elastic  fluid,  and  sometimes  even  more,  is  phlogistic 
air,  the  residue,  pure  acidulous  gas. 

Obs.  7.  The  residuary  lime  of  forty-eight  ounces  of  chalk,  heated 
to  the  total  expulsion  of  the  elastic  fluids,  weighs  only  twenty-seven 
ounces,  when  red-hot,  but  when  cool  it  weighs  more,  by  reason  of  the 
air  which  it  absorbs  as  the  heat  escapes  from  it. 

Obs.  8.  When  no  more  heat  is  employed  than  necessary  to  expel 
these  elastic  fluids,  the  residuary  matter  is  sensibly  diminished  in 
volume,  and  is  good  lime,  though  not  so  white  as  lime  prepared  in 
the  usual  way ;  it  slakes  readily  with  water,  and  grows  very  hot  and 
perfectly  white.  The  slaked  powder  is  exceedingly  fine,  except  from 
those  parts  of  the  lime  which  lay  in  contact  with  the  retort,  which  are 
always  superficially  vitrified,  because  clay  and  lime  promote  the  vitrifi- 
ation  of  each  other. 

Obs.  9.  The  lumps  of  this  lime,  immersed  in  lime-water,  or  boiling 


COMPONENTS  OF  MORTAR. 


9 


water,  to  expel  the  air  which  such  spongy  bodies  imbibe  in  cooling, 
dissolve  in  marine  acid  without  signs  of  effervescence. 

Obs.  10.  Limestone  or  chalk,  gradually  heated  in  a  crucible,  or  on 
the  bed  of  a  reverbatory  furnace,  or  in  contact  with  the  fuel  in  a 
wind  furnace,  does  not  become  perfectly  non-effervescent,  and  similar 
to  the  lime  last  described  in  slaking  instantly,  and  in  growing 
hissing  hot  when  water  is  sprinkled  on  it,  until  it  has,  after  a  strong 
red  heat  of  six  or  eight  hours,  sustained  a  white  heat  for  an  hour  or 
more — by  a  white  heat,  that  which  will  melt  cast  iron  is  meant. 

Obs.  11.  Limestones  heated  sufficiently  to  reduce  them  to  lime 
which  slakes  instantly,  and  is  perfectly  non-effervescent,  do  not  lose 
in  general  so  much  of  their  weight  as  chalkstone  does  under  the 
like  treatment.  Some  limestones  lose  little  more  than  a  third  of 
their  weight ;  those  which  lose  the  most  slake  the  quickest,  and  to  the 
finest  powder ;  but  those  which  lose  the  least  slake  the  slowest,  to  a 
gritty  powder,  composed  of  true  lime,  and  particles,  chiefly  gypseous. 

Obs.  12.  The  quantity  of  gypsum,  or  other  earthy  matter,  in 
well  burned  lime,  is  discoverable  by  weak  marine  acid,  which  dis- 
solves and  washes  away  the  lime,  leaving  the  gypsum  to  be  meas- 
ured when  dry,  the  portion  of  which  dissolved  with  the  lime  being  too 
small  to  notice,  and  if  any  other  earthy  or  saline  matter  existed  in 
the  limestone  it  vitrifies  (with  part  of  the  calcareous  matter)  in  the 
heat  necessary  for  making  non-effervescent  lime,  and  is  separable  by 
the  means  last  described,  and  in  most  instances,  even  by  a  fine  sieve. 

Obs.  13.  When  limestone  or  chalk  is  suddenly  heated  to  the  high- 
est degree  before  mentioned,  it  vitrifies  in  those  parts  which  touch 
the  furnace  or  fire- vessel,  or  the  fuel,  and  such  portions  become  incapa^ 
ble  of  slaking  freely,  or  making  good  lime,  and  limestone  is  the 
more  apt  to  vitrify  in  such  circumstances  in  proportion  as  it  contains 
more  gypseous  or  argillaceous  particles  ;  and  oysters,  or  cockle  shells, 
vitrify  more  easily  than  limestone  or  chalk,  when  they  are  suddenly 
heated,  which  is  imputed  to  their  saline  matter,  for  when  they  have 
been  long  exposed  to  the  weather  they  do  not  so  easily  vitrify. 


10 


OF  SAND. 


Obs.  14.  The  agency  of  air  is  no  further  necessary  in  the  pre* 
paration  of  lime  than  as  it  operates  in  the  combustion  of  the  fuel. 

Obs.  15.  Calcareous  stones  acquire  the  properties  of  lime  in  the 
highest  degree  when  they  are  slowly  heated  in  small  fragments 
until  they  appear  to  glow  with  a  white  heat,  when  this  is  continued 
until  they  become  non-effervescent,  but  is  not  augmented.  The  art 
of  preparing  good  lime  consists  chiefly  in  these  particulars,  and  as  be- 
fore remarked,  the  agency  of  air  is  no  further  necessary  than  to  pro- 
mote the  combustion  of  the  fuel. 

Obs.  16.  That  lime  is  to  be  accounted  the  purest  and  most 
suited  for  experiment,  whether  it  be  the  best  for  mortar  or  not, 
which  slakes  the  quickest,  heats  the  most,  is  whitest  and  finest  when 
slaked,  which,  when  wetted  with  lime-water,  dissolves  in  marine  acid 
or  distilled  vinegar  without  effervescence,  and  leaves  behind  the  small- 
est quantity  of  residuary  undissolved  matter. 

Obs.  17.  The  quick  slaking,  the  color  of  the  slaked  powder,  and 
the  former  acid  are  the  most  convenient  and  perhaps  the  best  tests 
of  the  purity  of  the  lime ;  the  whiteness  denotes  the  lime  to  be  free 
from  metallic  impregnation,  and  the  others  show  any  imperfection  in 
the  operation  of  burning,  and  the  heterogeneous  matter  inseparable 
from  the  calcareous  earth  by  burning. 

The  mode  of  slaking  lime,  and  the  relative  quantities  to  be  em- 
ployed in  the  composition  of  mortars  will  be  hereafter  explained. 

OF  SAND. 

There  are  three  distinct  species  in  use  for  building  purposes,  viz. : 
fiver  sand,  pit  sand,  and  sea  sand ;  but  of  these  the  two  former  should 
only  be  admitted  into  the  composition  of  mortar,  and  the  latter  is 
chiefly  adapted  for  hydraulic  cements,  or  such  as  will  indurate  under 
water,  as  applied  to  the  construction  of  marine  works — it  should  be 
pertinaciously  excluded  and  rejected  for  any  other  purpose,  and  even 
in  the  most  pressing  emergency  should  not  be  employed  as  an  ingredi- 


OF  SAND. 


11 


ent  of  mortar,  unless  it  has  been  previously  well  washed  in  fresh 
water  to  dissolve  and  dissipate  all  the  saline  and  other  objectionable 
matter,  otherwise  the  mortar  made  with  it  will  never  projoerly  harden, 
and  will  always  imbibe  the  slightest  humidity  which  may  be  present 
in  the  atmosphere  or  elsewhere,  and  conduct  it  through  the  work  to 
its  great  damage  and  disfigurement. 

There  is,  however,  another  ingredient  used  by  many  builders  in  heu 
of  either  of  the  former,  which,  although  when  properly  cleansed  and 
prepared,  assimulates  very  closely  thereto,  viz. :  road-drifts,  or  the 
fractional  particles  of  quartoze,  granite,  or  other  stones,  broken  off  or 
detached  by  abrasion,  or  attrition,  or  by  the  traffic  of  the  road :  this, 
though,  strictly  speaking,  not  belonging  to  the  category  of  building 
sands,  is  yet  a  very  fair  substitute,  and  recommends  itself  upon  the 
score  of  economy ;  and,  in  cases  where  the  former  two  species  cannot 
be  readily  or  cheaply  obtained,  is  allowable. 

But  whatever  variety  of  sand  is  employed  in  the  composition  of 
mortar  or  cements,  it  should  be  of  a  hard,  gritty,  and  granular 
nature ;  angular,  and  having  a  polished  surface ;  should  be  of  nearly 
uniform  size,  and  perfectly  freed  by  ample  washings  (in  clean  water), 
and  screenings  from  all  organic  matter,  alluvium,  salts  and  other 
foreign  and  injurious  substances,  which  interrupt  the  perfect  cohesion 
of  its  particles,  and  by  their  decomposition  bring  on  a  speedy  destruc- 
tion to  the  work.  Sand  when  perfectly  fit  to  be  used  in  mortar,  will 
bear  the  test  of  being  rubbed  between  the  hands  without  soiling  them, 
and  be  free  from  any  particular  odor ;  these  are  good  criterions  of 
the  purity  of  the  sand — a  most  important  matter  to  be  attended  to. 

Dr.  Higgins,  in  the  12th  section  of  his  treatise  before  referred  to, 
entitled,  Experiments  showing  the  best  kinds  and  mixtures  of  sands, 
and  the  best  method  of  using  the  lime-water  in  making  mortar," 
writes  thus  upon  the  subject  of  sands,  viz.:  Pursuing  the  analogy 
intimated  in  the  9th  section,  I  thought  that  as  large  stones  with 
curvilinear  faces,  imbedded  in  common  mortar,  do  not  form  so  strong 
a  wall  as  they  may  when  their  interstices  are  filled  with  stones  fittmg 


12 


OF  SAND. 


together  with  a  due  quantity  of  mortar,  so  mortar  made  with  sand 
whose  grains  are  nearly  equal  in  size,  and  globular,  cannot  be  so 
strong  at  any  period  of  induration,  as  that  which  is  mixed  with  as 
much  fine  sand  as  can  easily  be  received  into  its  interstices,  in  order 
that  the  lime  may  cement  the  grains  by  the  greater  number  and  ex- 
tent of  their  contiguous  surfaces."  And  he  further  adds:  *'It  is  to 
be  observed  that  the  sand  which  can  pass  through  a  sieve  in  washing^ 
is  considered  finer  than  that  which  may  be  sifted  through  the  same 
sieve  when  dry." 

Sand  is  non-absorbent,  that  is,  its  volume  is  not  increased  by  mois- 
ture, nor  contracted  by  drought  or  heat,  and  its  nature  is  imperish- 
able, as  is  daily  visible  on  the  sea-shore,  in  the  pit,  or  elsewhere,  and 
its  durability  can  be  proved  by  a  close  inspection  of  specimens  of  mor- 
tar which  have  withstood  the  wear  and  tear  of  ages,  and  its  character 
and  purity  are  not  less  important  than  that  of  lime,  in  the  composition 
of  mortar.  Of  the  proportions  of  sand  to  be  used  for  various  building 
purposes,  due  mention  will  be  made  when  treating  upon  the  prepara- 
tion of  mortar. 

The  following  interesting  experiments  upon  sand,  are  extracted 
from  Dr.  Higgins'  work  before  mentioned.  In  section  3,  he  says:  "I 
cleansed  a  large  quantity  of  '  Thames'  sand,  by  washing  it  in  stream- 
ing water,  and  sorted  it  into  three  parcels ;  the  coarsest  which  I  call 
rubble,  consisted  of  small  pebbles,  fragments  of  weathered  shells,  and 
grains  of  sand  of  divers  sizes,  which  in  washing  had  passed  through  a 
sieve,  whose  apertures  were  one-eighth  of  an  inch  square,  but  could 
not  pass  through  a  brass  wired  sieve  whose  meshes  were  one-sixteenth 
of  an  inch  square,  or  rather  more ;  the  next  parcel,  which  I  called 
fine  sand,  consisted  of  grains  of  divers  sizes,  which  in  washing  passed 
through  a  sieve  whose  meshes  were  one  thirty-second  of  an  inch  square ; 
the  third  parcel  consisted  of  grains,  the  largest  of  which  were  washed 
through  the  coarsest  sieve,  and  the  smallest  of  those  which  were  re- 
tained on  the  fine  sieve ;  these  I  call  coarse  sand. 

Having  dried  these  parcels  on  a  sand  plate,  and  provided  a  narrow* 


OF  SAND. 


13 


mouthed  glass  bottle,  capable  of  holding  about  two  ounces,  troy,  of 
water,  and  a  cylindrical  glass  vessel,  which  contained  twelve  of  these 
measures,  I  found  by  repeated  trials,  that  the  large  vessel,  charged  to 
the  brim  with  my  rubble,  might  be  made  to  hold  somewhat  more  than 
one  additional  measure  of  it,  when  the  rubble  was  well-packed,  by 
striking  the  bottom  of  the  vessel  repeatedly  against  the  table  perpen- 
dicularly. 

"Charging  the  same  vessel  with  coarse  sand,  I  could,  by  the  same 
treatment,  make  it  hold  two-thirds  of  the  thirteenth  measure ;  and 
twelve  measures  of  fine  sand  were  so  far  contracted  by  this  motion  of 
the  vessel,  that  it  could  hold  one  measure  and  one-fourth  more,  or 
thirteen  and  one-fourth  in  all.  After  noting  how  far  the  intersticial 
spaces  in  each  sized  sand  can  be  lessened  by  packing,  I  used  water  to 
show  what  proportion  these  bear  to  the  solids  in  these  diiferent 
sands.  I  found  that  the  thirteen  measures  of  rubble  which  I  stowed 
into  the  glass  cylinder  could  take  in  five  measures  of  water,  without 
any  increase  of  bulk ;  or  rather  with  a  striking  decrease  of  bulk : 
the  twelve  measures  and  two-thirds  of  stowed  coarse  sand  imbibed 
four  and  one  half  of  water,  and  yet  decreased  sensibly  in  bulk :  and 
the  thirteen  measures  and  one  fourth  of  fine  sand,  packed,  could  drink 
in  only  four  measures  of  water ;  but  the  diminution  of  bulk  was  more 
considerable  in  this  than  in  either  of  the  former,  for  the  sand  and 
water  together  measured  less  by  one-seventeenth  than  the  packed 
sand  alone." 

The  importance  of  the  foregoing  experiments  will  be  hereafter  shown 
and  explained.  The  Doctor  then  proceeds  to  say:  "When  sand 
was  poured  into  the  glass  cylinder  until  it  was  filled,  and  the  water 
added  before  the  sand  was  packed,  by  a  slight  agitation  of  the  vessel 
the  sand  contracted  in  a  much  greater  degree  than  is  above  expressed. 
Upon  the  whole  it  seemed  that  water,  by  poising  the  grains,  facilitates 
their  sliding  on  each  other,  to  fit  well  and  fill  the  spaces. 

"Until  I  had  made  these  experiments  I  did  not  well  understand,  how 
the  beating  of  new  mortar  makes  it  much  wetter,  and  more  plastic 


14 


OF  SAND. 


withal,  than  it  can  be  made  with  the  same  proportions  of  water  and 
solids,  by  mere  admixture.  I  now  perceived  that  heating  produces  this 
effect  by  closing  the  interstices  of  the  sand,  and  rendering  a  small 
quantity  of  lime  paste  as  effectual  towards  filling  them,  and  holding 
the  grains  together  to  form  a  plastic  mass,  as  a  greater  quantity  is,  in 
sand  whose  grains  cannot  fit  each  other  so  well. 

Seeing  that  the  intersticial  spaces  in  sand  are  so  greatly  lessened  by 
wetting  it,  I  judged  it  expedient,  for  this  reason  alone,  to  expend  all 
the  water  I  should  henceforth  use  in  making  mortar,  in  wetting  the 
sand  completely.  I  afterwards  observed  another  advantage  arising 
from  this  practice :  for  in  filling  the  spaces  with  the  fluid,  the  air  is 
easily  expelled,  and  the  lime  equally  diffused  in  them  by  a  little  heat- 
ing ;  but  when  the  water  is  added  to  a  mixture  of  lime  powder  and 
sand,  the  air  is  entangled  in  the  lime  paste,  and  cannot  without 
a  great  deal  of  heating,  be  totally  pressed  out  of  the  plastic  mass.  I 
likewise  found  that,  as  an  excess  of  water  is  injurious  to  mortar,  this 
is  an  excellent  method  of  regulating  the  quantity  of  it ;  for  the  portion 
of  lime  water  which  fills  the  spaces  in  sand,  and  can  be  held  by  capil- 
lary attraction  in  a  flat  heap  of  it,  is  precisely  the  quantity  which 
makes  well-tempered  mortar  with  one  part  of  the  best  slaked  lime,  and 
seven  of  the  best  sand. 

''As  I  experienced  some  difficulty  in  expelling  the  air  bubbles  out  of 
the  sand  wetted  in  my  deep  cylindrical  measure,  even  when  I  stirred 
up  the  miiss  with  a  slender  instrument,  I  concluded  that  the  spaces  in 
sand  are  rather  in  a  higher  proportion  to  the  solid  substance  of  it 
than  they  appeared  in  these  trials ;  so  that  we  may  say  they  are  at 
least  one-third  and  more  of  any  measure  of  the  fine  sand,  greater  in 
coarse  sand,  and  more  so  in  rubble. 

"Suspecting  on  another  ground  that  these  experiments  did  not  shovz 
the  whole  of  the  spaces  in  sand,  because  water  tends  to  insinuate  itself 
between  the  contiguous  surfaces  of  the  grains,  and  consequently  to  re- 
move them  asunder,  even  whilst  it  arranges  them,  I  attempted  to  as- 
certain the  proportion  of  these  spaces  to  the  solids,  by  another  method 


OF  SAND. 


15 


founded  on  this  supposition,  that  the  measured  portion  of  sand  which 
weighs  the  most,  has  the  smallest  quantity  of  intersticial  space. 

"By  experiment  I  found  that  a  well-packed  measure  of  the  rubble 
weighed  twenty  ounces  three  pennyweights :  the  like  measure  of  the 
coarse  sand,  packed,  weighed  twenty-one  ounces  eighteen  penny- 
weights :  and  the  same  quantity,  by  measure  of  the  fine  sand,  weighed 
twenty-three  ounces  two  pennyweights  and  three  grains. 

*'This  trial  corresponds  sufiiciently  with  the  former  in  showing  that 
the  sum  of  the  spaces  in  the  rubble  is  much  greater  than  that  in  the 
coarse  sand,  and  that  the  spaces  in  the  latter,  are  larger  in  the  sum 
than  those  of  the  fine  sand. 

''In  order  to  learn  whether  this  proportion  is  maintained  in  all  kinds 
of  sand,  I  tried  by  water  and  by  weight  in  the  foregoing  manner,  a 
great  number  of  the  sands  used  in  London,  such  as  the  coarsest  glass- 
grinder's  sand,  Hampstead  sand,  Lynn  sand,  fine  house  sand,  &c^ 
The  result  of  these  experiments  taught  me  that  the  spaces  are  always 
smaller  as  the  sand  is  finer,  provided  the  comparison  be  made  between 
the  sorted  fine  parts  and  the  coarsest  part  of  any  kind  of  sand ;  but 
this  does  not  hold  true  in  the  comparison  of  fine  sand  and  coarse  sand 
of  different  districts. 

''On  examining  the  several  specimens  of  sand  with  a  lens,  I  perceived 
that,  in  some,  the  grains,  however  different  in  figure,  were  bounded 
by  flat  faces  meeting  each  other  in  angles,  whilst  in  others  the  faces 
were  generally  rounded,  and  their  figures  such  as  the  foregoing  grains 
would  be  reduced  to,  by  grinding  off*  their  angles.  The  first  kind  I 
call  sharp  sand,  the  other,  round  sand.  Then  taking  into  considera- 
tion the  measurement  already  described,  together  with  the  sharphess 
or  roundness  of  the  sand,  I  found  that  the  spaces  are,  in  diffbrent 
kinds  of  sand,  as  the  size  and  roundness  of  them  compounded,  but 
they  don't  appear  to  be  smaller  in  any  kind  of  sand  that  I  have  seen, 
than  in  one  fine  parcel  of  Thames  sand,  which  I  think  is  owing  to  its 
being  sharper  than  any  of  the  finer  sands  which  I  had  compared  it 
with.    The  measure  which  contained  twenty-three  ounces  two  penny- 


16 


OF  SAND. 


weights  twelve  grains  of  the  fine  Thames  sand,  contained  only  twenty- 
two  ounces  ten  pennyweights  of  the  Lynn  sand,  which  is  a  great  deal 
finer,  but  rounder. 

**Ha\ing  thus  found  the  kind  of  sand  which,  by  reason  of  the  size 
and  figure  of  the  grains,  has  the  smallest  intersticial  space ;  I  next 
endeavored  to  ascertain  the  mixture  of  coarse  and  fine  sand,  which 
lessens  this  space  in  the  greatest  degree,  which  therefore  requires  the 
less  lime  to  cement  the  grains  together,  and  for  the  reasons  already 
mentioned,  promises  to  make  the  hardest  and  most  durable  cement. 

*'I  found  that  nine  measures  of  the  shingle,  and  an  equal  quantity 
of  the  fine  sand,  both  well  packed,  measured,  when  mixed  and  stowed 
closely,  sixteen  measures  and  one  eighth ;  that  eighteen  measures  of 
the  shingle,  and  nine  of  the  fine  sand,  tried  in  the  same  way, 
measured  twenty-four ;  and  that  on  mixing  the  shingle  and  fine  sand 
in  various  proportions,  nine  measures  of  shingle  took  into  its  inter- 
stices one  measure  and  one-half  of  the  fine  sand  without  any  increase 
of  bulk. 

"I  next  learnt  that  nine  measures  of  the  coarse  sand,  and  nine  of 
the  fine,  measured  in  like  manner  seventeen  and  a  half;  that  eighteen 
such  measures  of  coarse  sand,  well  mixed  with  nine  of  the  fine  sand, 
measured  twenty-six,  and  that  on  mixing  these  sands  in  various  pro- 
portions, eighteen  measures  of  the  coarse  sand  took  into  its  interstices 
one  measure  of  the  fine  sand  without  any  increase  of  bulk. 

*'  Lastly,  I  found  that  eighteen  such  measures  of  the  coarse  sand,  and 
nine  of  Lynn  sand,  which  is  much  finer  grained  than  the  foregoing, 
measured  twenty-four  when  well  mixed  and  stowed;  and  that  on 
mixing  them  in  various  other  proportions,  nine  measures  of  coai*se 
sand  took  into  its  interstices  one  and  a  half  of  the  Lynn  sand. 

**By  these  and  a  variety  of  similar  experiments  made  on  different 
sands,  I  found  that  the  quantity  of  fine  sand  taken  into  the  inter- 
stices of  the  coarse  sand  was  the  greater  without  increase  of  bulk,  as 
the  grains  of  the  coarse  differed  more  from  those  of  the  fine  in  bulk, 
provided  the  diameters  of  the  grains  of  coarse  sand  did  not  in  general 


OF  SAND. 


17 


exceed  those  of  the  fine  in  a  proportion  greater  than  five  to  one ;  that 
tlie  greatest  quantity  of  fine  sand  which  could  be  taken  into  the  inter- 
stices of  coarse  sand  was  one-sixth  of  the  bulk  of  the  coarse  sand,  and 
that  in  general  the  mixture  of  six  measures  of  coarse  sand  with  one 
of  the  finest  sand,  reduced  the  sum  of  the  intersticial  spaces  to  nearly 
one-half  of  the  quantity  of  them  in  coarse  only,  or  in  fine  Thames 
sand  or  rubble  only. 

"Instructed  by  these  observations,  I  proceeded  to  the  following 
experiments,  in  order  to  learn  the  advantages  or  defects  attending  each 
kind  of  sand,  and  how  far  my  expectations  from  the  art  of  lessening 
the  spaces, were  well  founded. 

"I  made  several  parcels  of  mortar  with  my  chalk-lime,  lime-water, 
and  rubble  in  different  proportions  ;  the  quantity  of  lime  being  in  one, 
a  fourth  of  that  of  the  rubble,  in  another  only  one  seventh,  and  in 
the  others  intermediate :  I  also  made  other  parcels  of  mortar  with 
my  chalk-lime,  lime-water,  and  the  coarse  sand ;  and  others  with 
this  lime,  lime-water,  and  fine  Thames  sand,  in  the  last  mentioned 
proportions. 

"I  next  made  a  great  variety  of  specimens  of  mortar,  some  of 
which  consisted  of  rubble  and  coarse  sand  mixed  in  different  propor- 
tions, wetted  with  lime-water,  and  blended  with  one-fourth,  or  one- 
seventh,  or  intermediate  quantities  of  lime  ;  others  were  composed  of 
similar  mixtures  of  rubble  and  fine  sand,  with  lime  and  lime-water; 
and  others  consisted  of  rubble,  coarse  sand,  and  fine  sand,  mixed  in 
different  proportions,  wetted  with  lime-water,  and  beaten  up  with  the 
different  quantities  of  lime  lately  mentioned. 

"I  spread  a  part  of  each  of  these  specimens  of  mortar,  as  soon  as 
it  was  made,  on  a  tile  soaked  in  lime-water,  half  an  inch  thick  in 
some  places,  and  much  thinner  in  others  ;  I  placed  the  remainder  of 
it,  formed  into  oblong  pieces  about  an  inch  in  diameter,  on  the  part 
of  the  tile  which  was  not  covered  with  mortar ;  and  I  set  all  the  tiles 
(numerically  marked)  in  the  situation  formerly  described,  where  they 
were  equally  exposed  to  the  weather ;  during  the  succeeding  twelve 


18 


OF  SAND. 


months  I  examined  each  specimen,  and  noted  my  obsen^ations,  the 
most  useful  of  which  I  shall  endeavor  to  relate  in  a  few  words. 

"The  specimens  containing  rubble  and  lime,  mixed  in  any  proportion 
greater  than  five  to  one,  were  not  fat  enough,  when  fresh,  to  be  conveni- 
ently used  in  building  or  stuccoing ;  but  none  of  them,  not  even  except- 
ing those  which  contained  the  greater  quantities  of  lime,  cracked  in  dry- 
ing. Those  which  had  the  least  quantity  of  lime  in  them  were  very 
rough  on  the  surface,  coarse  in  the  grain,  spongy,  and  easily  broken ; 
they  showed  a  defect  of  lime,  because  those  which  contained  more 
lime  were  not  so  bad  in  these  respects.  By  all  of  which  it  appeared 
that  whenever  such  rubble  must  be  used  for  want  of  sand  or  finer 
gravel,  the  lime  mixed  with  it  must  not  be  less  than  one-fifth  of  the 
quantity  of  rubble. 

**0f  the  specimens  consisting  of  coarse  sand  and  lime,  those  which 
had  the  smaller  quantities  of  lime,  were  too  short  for  common  use, 
and  could  not  be  made  to  assume  a  close  and  smooth  surface  whilst 
fresh,  but  in  drying  and  hardening,  they  were  in  every  respect  prefer- 
able to  the  cements  made  with  rubble  and  lime,  in  the  same  propor- 
tions ;  and  of  the  same  specimens  those  were  the  best  which  contained 
one  part  of  lime  in  five  ot  sand,  the  others  containing  less  lime,  being 
faulty,  like  those  made  with  rubble ;  and  those  in  which  lime  was 
mixed  in  much  greater  quantity  poslsessed  the  faults  often  observed  to 
attend  the  excess  of  lime. 

**The  specimens  which  consisted  of  fine  sand  and  lime  were  in  gene- 
ral better  than  the  foregoing,  and  that,  particularly,  which  contained 
one  of  lime  in  six  and  a  half  of  sand,  was  in  all  respects  much  better 
than  those  made  with  the  same  or  any  other  quantities  of  rubble  and 
lime,  and  coarse  sand  and  lime.  The  specimen  which  was  formed 
with  seven  parts  of  fine  sand  and  one  of  lime,  was  not  so  compact  and 
hard  as  that  last  mentioned.  The  comparison  of  these  two  showed 
that  seven  of  sand  are  too  much  for  one  part  of  lime,  when  the  sand 
is  fine  and  unmixed  with  coarse  grains.  The  specimen  made  with 
four  parts  of  fine  sand  and  one  of  lime,  had  the  noted  faults  attending 


OF  SAND. 


19 


the  excess  of  lime ;  for  it  cracked  in  drpng,  and  was  sensibly  injured 
in  the  winter,  by  those  alternations  of  drying,  wetting,  freezing  and 
thafwing,  formerly  noticed. 

'*0n  divers  comparisons  of  those  portions  of  mortar  made  of  fine  sand 
and  lime  with  the  former,  I  was  persuaded  that  a  better  cement  can  be 
composed  with  such  sand  as  I  call  finc^  than  with  a  coarser  sand, 
whose  grains  are  all  larger  than  any  of  those  in  my  fine  sand,  pro\dded 
the  coarser  sand  be  not  much  sharper  than  all  I  have  yet  seen.  If  my 
experiments  had  been  made  in  slow  succession,  this  last  observation 
would  have  led  me  to  imagine  that  the  mortar  will  be  found  the  bet- 
ter, as  the  sand  is  finer." 

Of  the  observations  made  on  the  parcels  of  mortar,  consisting  of 
mixed  sands  and  lime,  those  which  follow  are  the  most  pertinent  to 
our  present  inquiry : — 

*' The  specimens  made  with  mixtures  of  rubble,  coarse  sand,  and 
different  quantities  of  lime,  resembled  those  made  vdth  rubble  and 
lime  in  similar  proportions,  when  the  rubble  was  predominant ;  and  I 
could  perceive  no  advantage  derived  from  the  mixture  of  the  rubble 
and  coarse  sand,  except  that  the  cement  was  somewhat  better,  as  the 
quantity  of  rubble  was  less,  relatively  to  the  quantity  of  sand  and 
lime ;  but  none  of  these  specimens  were  in  any  respect  so  good  as 
those  made  with  fine  sand  only. 

"Of  the  specimens  made  with  rubble  and  fine  sand,  that  was  the 
best  in  which  the  fine  sand  was  twice  the  quantity  of  the  rubble.  But 
I  could  not  perceive  that  any  of  these  specimens  were  preferable  to 
those  made  with  the  like  quantities  of  fine  sand  and  lime,  or  that 
any  considerable  advantage  is  gained  by  the  mixture  of  rubble  and 
fine  sand. 

'^Of  the  specimens  made  of  coarse  sand,  fine  sand,  and  lime,  those 
were  manifestly  the  best  which  consisted  of  four  parts  of  coarse  sand, 
three  of  fine,  and  one  part  or  a  little  more  of  lime ;  for,  while  fresh, 
they  were  more  plastic  than  the  others,  and  were  easily  made  to  as- 
sume a  smooth  surface,  they  were  not  disposed  to  crack  in  this 


20 


OF  SAND. 


method  of  drying,  they  were  not  at  all  injured  by  wet,  or  freez- 
ing, or  thawing ;  they  were  pretty  close  in  the  grain,  and  they  grew 
so  hard  in  the  course  of  nine  or  ten  months  as  to  resist  the  chisel,  or 
any  force  tending  to  break  the  oblong  pieces,  much  more  powerfully 
than  any  of  the  specimens  lately  mentioned  ;  I  noted  them  as  the  best 
specimens  of  mortar  that  I  had  ever  made,  and  one  part  of  lime,  in 
four  of  coarse  and  three  of  fine  sand,  to  be  a  better  proportion  than 
any  other  of  the  sands  and  lime,  for  incrustations. 

*'0f  the  various  samples  of  mortar  made  with  mixtures  of  the  rubble, 
coarse  sand,  and  fine  sand,  those  were  the  best  in  which  the  fine  sand 
was  equal  or  nearly  so,  in  quantity,  to  the  rubble  and  coarse  sand,  in 
whick  the  rubble  was  not  much  more  than  one-seventh  part  of  the 
quantity  of  both  sands,  and  in  which  the  weight  of  the  lime  was  one- 
seventh  of  the  weight  of  the  sand  and  rubble,  or  a  little  more ;  but 
these  specimens  when  fresh,  were  less  plastic  and  less  capable  of  as- 
suming a  smooth  surface  under  the  trowel,  as  the  quantity  of  the  rubble 
was  greater ;  and  I  could  not  find  that  they  were  preferable  in  any 
particular  to  those  respectively  which  were  made  with  similar  quan- 
tities of  lime  and  the  mixtures  of  coarse  and  fine  sand  lately  recom- 
mended. 

^ '  Upon  the  strictest  comparison,  I  concluded  that  one  part  of  rubble 
in  three  of  coarse  and  three  of  fine  sand,  makes  as  good  mortar  with 
lime  as  can  be  made  with  the  sand  and  lime  without  rubble,  for  any 
purpose  which  does  not  require  a  finer  cement,  but  there  is  no  advan- 
tage gained  by  the  use  of  rubble  when  the  coarse  and  fine  sand  can 
be  had  equally  cheap,  unless  a  rough  surface  be  required. 

*'In  stuccoing  walls,  the  rubble  promised  to  be  useful  in  pointing, 
and  in  the  first  coat,  because  a  roughness  of  this  coat  raakes  the  finer 
exterior  coat  adhere  more  firmly. 

*'In  the  review  of  all  these  specimens,  it  appeared  that  the  quantity 
of  lime  which  forms  a  mass  somewhat  plastic  with  sand  and  water,  is 
the  smallest  quantity  necessary  for  making  the  best  mortar  which  such 
sand  can  afford,  and  that  any  further  quantity  of  lime  is  useless  in 


OF  SAND. 


21 


the  coarser  sands,  and  injurious  in  the  finer :  that  the  necessary  plas- 
ticity is  induced  by  the  smaller  quantities  of  lime,  as  the  interstices  of 
the  sand  are  smaller  in  the  sum,  and  as  the  grains  fit  each  other  the 
better  in  consequence  of  the  due  mixture  of  coarse  and  fine  sands ; 
but  that  the  lessening  of  the  intersticial  spaces,  by  the  admixture  of 
fine  sand  with  the  coarse,  does  not  enable  us  to  lessen  the  quantity  of 
lime  so  far  as  might  be  expected,  in  consequence  of  our  notions  of  the 
spaces  measured  by  water.  It  seems  that  the  grains  of  fine  sand  are 
held  asunder  by  the  lime  paste,  to  a  greater  distance  than  they  are  by 
water,  and  that  the  reason  why  the  finer  sand  requires  more  lime  than 
the  coarser  and  mixed  sand,  is,  that  the  spaces  which  are  more  nume- 
rous in  fine  sand  than  in  the  coarse,  are  more  augmented  in  the  whole 
quantity  of  them,  by  the  particles  of  lime,  which  intercede  alike,  the 
coarse  and  fine  grains." 

Further  allusion  to  this  matter  will  be  subsequently  made.  Of 
the  several  species  of  sand  in  general  use  for  building  purposes,  that 
which  is  obtained  from  the  bottom  of  fresh  water  rivers,  or  from  the 
beds  of  rivulets  and  other  water-courses,  and  known  by  the  term 
*'silt"  is  unquestionably  the  best;  and  next  in  quality  is  pit-sand, 
but  this  is  in  general  too  fine,  and  not  so  sharp  and  gritty  as  the 
former. 

"Before  closing  these  observations  upon  sand,  it  may  be  useful  to 
remark  that,  in  cases  of  emergency  where  proper  sands  cannot  be  readily 
obtained,  ordinary  gravel — if  it  be  washed  from  all  impurities, 
clay,  &c.,  and  well  freed  from  all  large  round  pebbles,  and  its  par- 
ticles sub-di\ided  through  proper  sieves  into  two  or  three  gradations 
of  sizes,  viz. ;  coarse,  medium,  and  Jine — may  be  used  for  construc- 
tive purposes,  but  its  particles  being  round,  or  less  angular  than  ordi- 
nary sand,  do  not  so  readily  unite,  and  it  consequently  forms  or  pro- 
duces mortar  of  an  inferior  quality." 

The  foregoing  experiments  are  highly  valuable  and  important,  and 
evince  great  judgment,  clear  perception,  and  an  indomitable  perse- 
verance and  pertinacity  to  ascertain  facts  and  establish  truth,  and 


22  WATER. 

prove  to  a  demonstration  that  a  careful  selection  and  admixture  of 
coarse  and  fine  sands  in  certain  portions  are  preferable  for  mortar  or 
cements  than  any  sizes  employed  individually,  because  the  smaller 
grains  have  the  effect  of  filling  up  the  interstices  of  the  larger,  there- 
by tending  to  consolidate  the  mass  and  to  lessen  the  quantity  of  lime 
or  other  cementitious  matter  necessary  to  combine  the  whole.  They 
also  teach  that  it  is  far  preferable  to  apply  the  great  bulk  of  the  water 
to  the  sand  before  incorporating  it  with  lime,  instead  of  mixing  the 
two  ingredients  together  before  slaking  ;  that  by  this  method  the  air  is 
more  readily  and  freely  expelled  from  the  mass,  and  the  mortar  con- 
sequently becomes  considerably  improved.  These  results  have  been 
fully  confirmed  by  my  personal  experience  and  observation  during  a 
series  of  many  years  professional  practice  in  Em'ope  and  in  distant 
parts  of  the  globe,  and  I  have  generally  found  that  the  qnality  of 
mortar  (coeteris  paribus)  depends  chiefly  upon  the  purity  of  the  sand, 
the  form  of  its  grains,  and  a  due  admixture  of  two  or  more  differing 
sizes.  The  common  practice  of  using  unwashed  sands,  or  road-drift, 
argillaceous  loams,  and  even  alluvium  or  common  soil,  charged  as  it 
is  with  vegetable  and  organic  matter,  cannot  be  too  much  repre- 
hended, nor  too  speedily  abolished.  Builders  are  very  apt  to  com- 
pound their  mortar  with  the  soil  removed  from  the  foundations  of  the 
sites  of  their  buildings,  alike  regardless  of  its  quality,  or  suitability 
for  the  purpose,  or  of  the  natural  consequences  of  its  employment. 


WATER. 

The  last  ingredient  necessary  in  the  formation  of  mortar  is  the 
aqueous  element,  the  nature  of  which,  being  so  well  known  to  all, 
needs  no  description :  but  not  so  with  respect  to  its  components,  for 
the  value  or  quality  of  calcareous  cements  depends  considerably  upon 
the  purity  of  the  water.  It  must  in  all  cases  be  fresh,  and  obtained 
from  a  river,  pond,  spring,  well,  brook,  or  any  running  water-course, 
but  never  from  any  stagnant  pond  or  pool,  which  is  always  sur- 


WATER. 


23 


charged  with  vegetative  and  organic  matter ;  nor  should  it  be  obtained 
from  any  spring  or  well  which  is  oxydized  (i.  e.,  containing  mineral 
properties,  examples  of  which  are  often  to  be  met  with) ;  nor  should 
the  water  contain  any  chalybeate  or  other  chemical  components ;  and 
sea- water  is  objectionable  for  the  same  reasons  as  explained  in  refer- 
ence to  sand,  it  being  only  allowable  in  the  formation  of  hydraulic 
cements  or  marine  mortar.  Rain  water  is  good  if  not  kept  long 
enough  to  vegetate  or  vivify. 

Dr.  Higgins  has  the  following  remarks  upon  the  nature  and  use  of 
water  in  the  composition  of  cements,  aiid  recommends  the  use  ot 
lime-water  as  being  far  preferable.  In  section  7  of  his  work,  "On 
the  depreciation  of  mortar  by  the  common  method  of  using  water, 
and  of  the  use  of  lime-water,"  he  says:  "Einding  by  reason  and 
experience  the  advantage  of  totally  expelling  the  gas,  and  preventing 
the  return  of  it  to  lime,  or  even  to  mortar  before  it  is  used,  and 
knowing  that  common  water,  which  is  employed  in  great  quantities, 
first  in  slaking  limes  and  then  in  making  mortar,  contains  a  great 
deal  of  the  noxious  gas,  it  occurred  to  me  that  the  vulgar  process  of 
making  mortar  is,  in  this  fresh  instance,  injudicious,  as  it  tends  to 
injure  materials  otherwise  good. 

**Lime  is  slaked  in  such  a  manner  that  almost  the  whole  of  the 
water  is  evaporated,  and  contributes  nothing  to  the  mortar  except  so 
far  as  it  deposits  its  gas  in  the  lime,  and  injures  it ;  and  then  the 
slaked  dry  lime  and  the  sand  require  more  water  to  make  them  into 
mortar.  I  have  found  the  quantity  of  water  used  for  both  these  pur- 
poses to  be  twice  the  weight  of  the  lime  at  least.  The  quantities  of 
acidulous  gas  known  to  be  contained  in  the  waters  commonly  used 
in  making  mortar,  must  greatly  debase  the  lime  which  is  thus  ex- 
posed to  double  its  weight  of  such  water ;  and  upon  these  grounds  I 
was  assured,  a  priori,  that  it  would  be  a  considerable  improvement  in 
mortar  to  use  no  water  in  it  except  what  has  been  previously  freed 
from  acidulous  gas. 
"  This  is  done  in  making  lime-water^  the  use  of  which  appeared  ad  van- 


24 


WATER. 


tageons  in  another  point  of  view.  One  seven-hundredth  part  of  lime- 
water,  being  lime,  (according  to  the  experiments  of  Mr.  Brandt, 
which  I  find  to  be  true) ;  and  the  lime  being  introduced  in  a  state  of 
solution,  which  favors  the  crystallization  of  it  between  the  grains  of 
sand,  assists  in  cementing  them  together  by  the  utmost  attractive 
forces  of  its  parts,  if  my  notions  of  the  polarity  of  these  parts  be 
true. 

''I  made  divers  experiments  to  try  the  practical  validity  of  this 
reasoning,  and  found  it  to  be  true ;  for,  on  comparing  specimens  of 
mortar  made  with  my  best  lime,  slaked  with  river  water,  and  sand 
and  water,  and  spread  on  tiles  soaked  in  water,  with  other  specimens, 
made  with  the  same  proportions  of  lime,  slaked  with  lime-water,  and 
sand  and  lime-water,  and  spread  on  tiles  previously  soaked  in  lime- 
water,  the  latter,  at  every  stage  of  them,  were  sensibly  harder,  and 
they  adhered  to  the  tiles  better  than  the  former.  I  must  observe, 
however,  that  such  distinctions  (discoveries)  cannot  easily  be  made, 
except  by  those  who  have  a  great  deal  of  experience  in  these  trials  and 
comparisons.  On  repeated  examinations  of  these  and  my  other  speci- 
mens, I  was  highly  encouraged  in  my  pursuit,  for  those  made  with 
lime-water  were  better  near  the  surface  than  any  I  had  ever  made, 
and  I  had  good  reason  to  be  persuaded  that  the  extraordinary  indura- 
tion would  proceed  in  time,  through  the  whole  mass." 

From  the  above  experimental  results,  the  superiority  of  'Mime- 
water"  over  crude  water,  in  the  composition  of  mortar,  is  apparent, 
and  the  subsequent  experience  of  many  professional  gentlemen  fully 
confirms  the  said  theorem,  and  as  lime-water  is  easily  prepared,  even 
upon  a  large  scale,  by  dissolving  a  quantity  of  lime  in  large  casks  or 
tanks,  it  behooves  every  one  engaged  in  the  execution  of  extensive  and 
important  works  to  adopt  the  plan. 

Other  ingredients  are  sometimes  introduced  into  the  compositions 
of  mortar  for  particular  purposes  or  objects,  such  as  cinders,  scoria, 
iron  scales  or  filings,  crude  or  burnt  clay,  pulverized  potters'  ware,  or 
tiles,  or  other  porous  substances ;  they  must,  however,  be  pure  and  dry, 


VARIOUS  KINDS  OF  MORTAR. 


25 


and  rendered  pretty  fine  by  pulverization.  Of  these,  however,  we  shall 
have  occasion  to  speak  hereafter,  in  the  description  of  hydraulic  and 
other  cements  for  special  purposes. 

Of  the  Composition  of  various  kinds  of  Mortar,  their  Ap- 
plication AND  Respective  Values  ;  with  Occasional  Notes 
OF  the  Experiments  and  Opinions  of  Dr.  Higgins  and 
other  first-class  authorities. 

Mortar  as  before  mentioned,  is  generally  compoj<ed  of  three  in- 
gredients, viz. :  Lime  (or  cement),  Sand,  and  Water,  the  respective 
properties  of  which  may  be  defined  as  follows,  viz. : — 

1st.  Lime  is  the  cementing  ingredient.  2d.  Sand  is  the  substance 
or  matter  (as  relates  to  the  mortar  only)  to  be  combined.  3d.  Water 
IS  the  element  by  which  the  combination  of  the  lime  and  sand  is  to  be 
accomplished. 

Such  being  the  relative  uses  and  properties  of  the  above  mentioned 
ingredients,  we  must  consider  that  lime  being  the  cementitious  med- 
ium, and  the  particles  of  sand  the  material  to  be  united,  through  the 
agency  or  intervention  of  water,  that  it  will  require  in  the  compostion 
of  the  mortar  no  more  of  the  aqueous  element  than  wUl  efiectually 
slake  or  dissolve  the  lime  into  a  liquid  paste,  or  make  it  free  and  con- 
venient for  use ;  and  that  of  this  cementitious  paste,  no  greater  quan- 
tity wUl  be  necessary  than  sufficient  to  conjoin  or  unite  the  several 
sides  or  angles  of  the  sand  together,  or  what  is  analogous,  to  fill  the 
mterstices  between  their  bodies ;  and  that  the  more  effectually  this  can 
be  done,  the  more  compact  and  durable  will  be  the  mortar,  the  more 
excluded  will  be  all  damps  and  other  atmospheric  influences,  and  con- 
sequently the  prevention  of  those  destructive  forces  "  expansion  and 
contraction."  This  important  desideratum  can  only  be  obtained  by  a 
judicious  proportion  and  combination  of  the  several  component  in- 
gredients, and  which  Dr.  Higgins  and  other  qualified  experimentors 

have  already  shown  to  be,  with  pure  materials  (et  caeteris  paribus)^  to 
2 


26 


VARIOUS  KINDS  OF  MORTAR. 


be  one  part  of  lime  to  five,  six,  or  seven  parts  of  sand — the  relative 
proportion  of  the  latter  ingredient  being  dependent  upon  its  descrip- 
tion, and  guage  or  size ;  because  pit  sand  will  require  more  lime  (to 
make  an  equally  good  mortar)  than  sharp  river  sand,  or  clear  road 
drift,  and  coarse  sand  will  take  less  lime  than  fine  sand,  although  ob- 
tained from  the  same  source.  This  fact  or  knowledge  resulted  from 
the  experiments  of  Dr.  Higgins,  before  quoted,  and  proves  the  practi- 
cal value  of  them.  But  where  an  undue  or  unnecessary  quantity  of 
lime  is  employed,  the  result  will  be,  less  compactness  or  solidity,  im- 
perfect induration,  a  disposition  to  imbibe  and  retain  all  moisture,  and 
to  sympathize  with  every  atmospheric  change ;  a  constant  disposition 
to  expand  and  contract,  and  consequent  liability  to  a  more  speedy  decay. 

With  a  view  to  determine  the  question  or  fact.  Dr.  Higgins  made 
a  series  of  impartial  experiments,  the  result  of  which  he  gives  as  fol- 
lows, in  section  8  of  his  said  treatise  on  calcareous  cements,  entitled, 
* '  Experiments  made  with  a  view  to  approximate  the  best  proportions 
of  lime,  sand,  and  water  for  mortar"  : — 

"In  reading  over  my  notes,  and  examining  the  specimens  of  mor- 
tar which  I  had  hitherto  made,  I  perceived  that  those  were  the  best 
which  being  made  with  common  fresh  lime,  or  with  well-burnt  lime, 
contained  the  least  of  it ;  that  is,  one  ounce  of  lime  in  six  or  more  of 
sand ;  and  finding  that  this  quantity  of  lime  to  be  much  less  than 
commonly  used  in  making  mortar ;  and  suspecting  that  as  a  wall  may 
be  the  weaker  for  its  containing  too  much  mortar  (which  widens  the 
joints),  so  mortar  may  be  weakened  by  the  introduction  of  more 
lime  than  is  necessary  to  cement  the  grains  of  sand  together.  I 
thought  another  cause  of  the  defect  of  common  mortar  opened  to  my 
view,  and  that  it  was  advisable  to  determine  by  experiment  the  best 
proportion  of  lime  and  sand  in  making  mortar  in  wliich  lime  water  is 
used. 

I  made  five  parcels  of  mortar  with  my  best  stone  lime,  recently 
slaked  with  lime-water  and  coarse  Thames  sand,  in  the  following  pro- 
portions, hy  weight : — 


VARIOUS  KINDS  OF  MORTAR. 


27 


No.  1, 
"  2, 
"  3, 
"  4, 


Slaked  Lime. 


1 
1 
1 
1 
1 


Saiid.  Water. 
5 

6      ^  quantity  sufficient. 


7 
8 


**This  latter  specimen  was  not  sufficiently  plastic  for  common  use, 
or  as  the  workmen  express  themselves,  it  was  too  shor-t.  I  further 
observed  that  the  quantity  of  water  required  to  make  mortar  to  the 
proper  temper  is  7nore  as  the  quantity  of  lime  is  greater,  relatively  to 
the  proportion  of  sand. 

* '  I  spread  these  specimens  on  tiles  in  the  month  of  J une,  and  ex- 
posed them  to  the  air  and  sun,  which  then  was  very  hot.  As  my 
former  experiments  taught  me  to  expect  that  some  of  these  in  hasty 
drying  would  crack  considerably,  and  as  mortar  in  building  is  not 
liable  to  dry  so  quickly  as  these  specimens,  in  order  to  render  the 
inferences  from  these  experiments  the  more  general,  I  made  five 
other  parcels  of  mortar  in  the  same  manner,  and  exposed  them  in  the 
same  way,  in  every  respect,  except  that  the  direct  rays  of  the  sun 
could  not  fall  upon  them,  or  heat  the  pavement  on  which  they  stood. 
In  three  days  I  found  this  necessary,  for  the  first  of  those  which  stood 
exposed  to  the  sun  cracked  considerably ;  the  second,  less ;  the  third 
sliowed  three  or  four  very  slender  fissures,  visible  only  on  a  very  close 
inspection ;  and  the  fourth  and  fifth  showed  no  cracks  at  this  time^ 
nor  in  a  month  afterwards,  when  the  fissures  of  the  other  were  con- 
siderably enlarged. 

Of  the  specimens  kept  in  the  shade,  and  examined  on  the  third 
day  like  the  former,  the  first  was  cracke'd  in  divers  parts  ;  the  second 
showed  two  or  three  very  slender  cracks,  and  the  rest  were  not  cracked 
in  the  least,  and  never  cracked  afterwards,  although  I  was  forced  to 
remove  them  to  the  place  where  the  others  stood. 

*'Thus  it  appeared  in  a  very  short  time  that  an  excess  of  lime  dis- 
poses mortar  to  crack,  and  consequently  injures  it ;  that  the  hishest 
proportion  of  lime  to  such  sand,  which  may  be  used  without  incurring 


9S  VARIOUS  KINDS  OF  MORTAE. 

this  risk  depends  on  the  circumstances  in  which  the  mortar  is  to  be 
exposed  ;  that  no  more  than  one  part  of  lime  to  seven  of  coarse  sand 
ought  to  be  used  in  mortar  which  is  to  dry  quickly,  and  less  lime  may 
not  be  used,  because  it  does  not  render  the  mass  sufficiently  plastic  for 
building  and  incrustation  ;  and  that  if  a  greater  proportion  of  lime  to 
such  sand  improves  the  mortar  in  any  respect,  it  is  to  be  used  only 
when  the  mortar  cannot  dry  so  quickly  as  it  did  in  the  specimens  ex- 
posed to  the  sun. 

In  the  course  of  nine  months  I  clearly  perceived  that  those  speci- 
mens which  stood  in  the  shade  for  the  first  three  days  were  harder 
and  better  in  other  respect  than  those  which  were  suddenly  exposed  to 
the  sun,  the  comparison  being  made  between  the  specimens  which 
contained  a  corresponding  proportion  of  lime,  and  which  cracked  the 
least  or  not  at  all,  and  of  all  the  specimens  those  were  the  best  which 
contained  one  part  of  lime  to  seven  of  sand ;  for  those  which  contain- 
ed less\im.Q,  and  were  too  short*'  while  fresh,  were  most  easily  cut  and 
broken,  and  were  pervious  to  water,  and  those  which  contained  more 
lime,  although  they  were  closer  in  the  grain,  did  not  harden  so  soon, 
or  to  so  great  a  degree,  even  when  they  escaped  cracking  by  lying  in 
the  shade  to  dry  slowly.  I  therefore  concluded,  that  hasty  drying 
injures  mortar  made  in  any  proportions  of  such  sand  and  the  best 
lime,  and  that  the  best  proportion  is  one  of  lime  in  seven  of  sand, 
whether  the  mortar  is  to  be  dried  quickly  or  not. 

*'  I  must  observe,  however,  that  these  conclusions  were  made  rather 
with  a  view  to  my  future  experiments,  in  which  an  approximation  to 
the  best  proportions  of  lime  and  sand,  and  the  best  treatment  of  the 
mortar  would  save  a  great  deal  of  trouble,  than  to  any  general  and 
invariable  rules  for  making  mortar. 

"I  reserved  it  to  be  mentioned  here,  that  I  set  apart  four  ounces 
of  each  of  the  foregoing  specimens  of  mortar,  and  spread  them  sever- 
ally on  plates  of  thin  window  glass,  to  the  thickness  of  a  quarter  of  an 
inch  or  thereabouts,  and  noted  the  weight  of  each  plate  with  its  speci- 
mens of  mortar  recently  made. 


VARIOUS  KINDS  OF  MORTAR. 


29 


"  These  being  eqimlly  exposed  to  the  sun,  and  weighed  at  different 
periods,  were  found  to  lose  weight  in  equal  times,  nearly  in  proportion 
to  the  quantity  of  lime  and  water  used  in  making  them ;  and  the 
smallest  loss  of  weight  when  the  specimens  were  perfectly  dry  and  con- 
siderably hardened,  was  one-tenth  of  the  weight  of  the  same  speci- 
mens recently  made. 

"In  my  former  experiments,  I  had  observed  that  mortar  which  sets 
without  cracking,  whether  owing  to  the  due  proportion  of  sand,  or  to 
the  slow  exhalation  of  the  water  from  mortar  containing  less  sand, 
never  cracks  afterwards,  whatever  other  faults  it  may  have  ;  and  the 
specimens  mentioned  in  this  section,  after  a  trial  of  eighteen  months 
afforded  the  same  observation. 

By  the  setting  of  mortar  I  mean  that  solidity  which  it  acquires  by 
mere  drying,  and  which  differs  widely  from  the  induration  that  takes 
place  in  time,  by  other  means  which  we  shall  hereafter  consider. 

"  Seeing  then  that  the  quantity  of  water  is  as  the  quantity  of  lime, 
— that  the  fissures  happen  only  in  the  drying  or  setting — that  the 
danger  of  cracking  is  greater,  not  merely  as  the  quantity  of  water  is 
greater  relatively  to  the  sand,  nor  merely  as  the  water  is  more  ex- 
peditiously exhaled,  but  in  a  rate  compounded  of  these;  I  inferred 
that  mortar  which  is  to  be  used  where  it  must  dry  quickly  ought  to 
be  made  as  stiff  as  the  purpose  wiU  admit,  that  is,  with  the  smallest 
practicable  quantity  of  water,  and  that  mortar  will  not  crack,  although 
the  lime  be  used  in  excessive  quantity ;  provided  it  be  made  stiffer,  or 
made  to  a  thicker  consistence  than  mortar  usually  is. 

*'This  inference  was  afterwards  confirmed,  for  specimens  made  thus 
with  one  part  of  lime  and  only  six  of  sand,  and  others  made  with 
greater  proportions  of  lime,  but  as  stiff  as  they  could  be  used,  did  not 
crack  in  any  exposure,  but  they  had  faults  which  will  be  hereafter 
noticed." 

Thus  far  the  above  described  experiments  fully  demonstrate  the 
advisability  of  employing  a  moderate  proportion  of  lime  and  water  to 
the  quantity  of  sand,  and  that  theory  I  have  found  correct  during 


80 


VARIOUS  KINDS  OF  MOETAR. 


many  years  of  professional  experience  in  Europe,  Australia  and  else- 
where, and  therefore  confidently  recommend  it  to  the  notice  and  trial 
of  all  persons  engaged  in  the  building  art,  in  further  allusion  to  which, 
the  Doctor  next  proceeds  (in  Section  9,)  to  consider  the  "Theory  of 
induration  dependent  on  the  proportion  of  lime  and  sand  in  mortar, 
and  observations  on  the  bad  effects  of  the  vulgar  proportions  of  these." 
Pie  says :  * '  It  is  sufficiently  known  that  the  aggregation  of  calcar- 
eous bodies,  which  burn  to  lime,  or  are  chiefly  composed  of  the  matter 
of  lime,  is  much  weaker  than  that  of  the  quartoze  (sand),  in  so  much 
that  the  steel  which  easily  cuts  all  calcareous  stones  or  spars,  is  as 
easily  cut  by  the  siliceous,  and  all  stones  and  powders  which  are 
chosen  for  cutting  and  grinding  steel  are  found  to  have  this  effect 
by  reason  of  their  siliceous  or  quartoze  particles.  This  being  consider- 
ed, together  with  divers  observations  heretofore  related,  I  reason  in  the 
subsequent  manner : — 

As  stones  are  cemented  together  in  walls  by  the  mediation  of 
mortar,  so  the  grains  of  sand  or  gravel  are  made  to  cohere  and  form  a 
solid  mass  of  mortar,  by  the  intervention  of  lime. 

**By  the  bare  inspection,  as  well  as  by  the  experienced  induration, 
one  part  of  lime  paste  appears  sufficient  to  intercede  the  grains  of 
seven  of  sand  without  interruption  of  continuity,  and  in  drying,  to  fill 
the  spaces  between  them,  or  to  attract  matter  enough  for  this  pur- 
pose from  the  air.  In  this  case  the  grains  cohere  at  the  smallest 
distances  of  them,  and  by  means  of  the  thinnest  laminae  of  cal- 
careous matter ;  and  such  mortar  is  the  stronger  as  it  consists  of  the 
greater  quantity  of  hard  quartoze  bodies,  cohering  by  means  of  the 
smallest  practicable  quantity  of  soft  and  brittle  calcareous  strata :  just 
in  the  same  manner  as  a  wall  built  with  porphyry  and  bad  mortar  is, 
(cceteris  paribus)  the  stronger  as  the  joints  are  made  thinner ;  for  all 
masses  of  such  structures  as  mortar  or  cementitious  walls  resist  frac- 
ture and  ruin,  with  the  powers  of  aggregation  which  are,  not  merely 
as  the  aggregate  of  the  stones  or  brick,  nor  barely  as  the  aggregate 
of  the  softer  cements,  but  in  a  ratio  compounded  of  these,  and  vary- 


VARIOUS  KINDS  OF  MORTAR. 


3t 


ing  with  circumstances  which  we  need  not  attend  to  at  present ;  and 
those  masses  therefore  will  resist  the  wind,  in  which  the  stronger  ag- 
gregates bear  the  greatest  proportion  to  the  weaker,  so  far  as  it  is  con- 
sistent with  the  continuity  of  them. 

Secondly.  The  small  stones  which  compose  a  heap  of  sand  do  not 
imbibe  water,  their  volume  is  not  increased  by  wetting  them,  nor  less- 
ened in  drying ;  neither  does  a  measure  of  wet  sand  contract  sensibly 
in  drying :  this  last  I  have  repeatedly  experienced  ;  but  small  pieces 
of  lime  are  considerably  increased  by  wetting  them ;  and  as  the  soft 
paste  of  lime  contracts  greatly  in  drying,  it  must  crack  in  every  part 
where  the  drying  paste  is  prevented,  by  its  adhesion  to  bodies  or  by 
other  causes,  from  contracting  uniformly  and  concentrically.  As  the 
contraction  of  mortar  in  drying,  and  its  consequent  cracking  depends 
on  the  lime  paste,  and  not  on  the  sand,  they  must  take  place  in  the 
greater  degree,  and  they  must  be  lessened  or  prevented  by  a  due  pro- 
portion of  sand,  which  proportion  experience  shows  (as  before  stated) 
to  be  seven  parts  of  sand  to  one  of  lime.  Thus  we  understand  the 
cause  of  cracking,  and  how  it  happens  that  this  defect  is  prevented  by 
using  less  than  the  customary  quantity  of  lime,  and,  although  the 
lime  should  be  used  in  excess,  by  using  less  than  the  customary  quan- 
tity of  water. 

''Thirdly.  The  more  perfect  and  expeditious  setting  and  induration 
of  mortar,  containing  only  one  part  of  lime  in  seven  of  sand,  than  of 
mortar  made  with  greater  proportions  of  lime,  may  be  deduced  from 
several  concurrent  causes.  Having  less  water  in  its  composition,  it  is 
sooner  saturated  with  the  matter  which  the  air  presents,  and  which 
seems  necessary  to  the  induration  of  mortar ;  and  in  this  saturation, 
the  swelling  of  the  lime  is  not  so  great  as  to  put  forth  and  derange 
the  grains  of  sand  after  they  have  once  been  placed,  and  in  some 
degree  cemented  together. 

"This  latter  inconvenience  arising  from  the  excess  of  lime,  cannot 
easily  happen  in  mortar  compressed  on  all  sides  in  massive  buildings, 
but  it  manifestly  occurs  in  the  exterior  parts  of  the  joints  in  walls. 


82 


VARIOUS  KINDS  OF  MORTAR. 


where  the  mortar  visibly  swells,  and  afterwards  crumbles ;  it  is  lik<v 
wise  visible  in  the  upper  parts  of  walls  of  modern  construction,  where 
the  swelling  is  not  prevented  by  a  superincumbent  weight.  In  these 
cases  the  joints  become  hollow ;  houses  lately  built  look  old  and  ruin- 
ous, and  the  bricks  themselves  being  bibulous  in  such  position,  soften 
and  moulder,  in  consequence  of  the  alternate  wetting,  drying,  freezing, 
and  thawing ;  these  being  effectual  agents  in  the  dissolution  of  all 
bodies  which  freely  imbibe  moisture. 

"  Without  awaiting  the  event  of  those  experiments  which  I  have 
lately  made  on  the  great  scale,  and  shall  point  out  before  I  conclude 
this  essay,  we  may  on  these  grounds  alone  assure  ourselves,  that  the 
strength  and  duration  of  calcareous  incrustations  composed  of  lime 
and  sand,  will  be  greater  as  we  depart  from  the  proportions  of  lime 
and  sand  commonly  observed,  approaching  to  that  of  one  part  of  lime  to 
seven  of  sand,  because  the  stucco  which  hardens  the  soonest  must  be 
the  least  injured,  whilst  it  is  new,  by  the  beating  rains  and  various 
accidental  impressions ;  because  that  which  adheres  the  most  firmly  to 
the  other  materials  of  buildings,  and  which  acquires  the  greatest  degree 
of  induration,  must  contribute  most  to  the  strength  of  the  walls,  and 
best  withstand  the  shocks,  attrition,  and  other  trials  to  which  the 
stucco  is  exposed ;  because  that  which  contains  the  greatest  proportion 
of  sand,  is  less  liable  to  be  injured  by  any  saline  matter  with  which 
the  air  is  sometimes  impregnated,  as  its  calcareous  matter  is  best  de- 
fended by  the  sand  ;  but  above  all,  because  the  stucco  made  with  one 
part  of  lime  and  about  seven  of  sand  is  not  disposed  to  crack,  for  in- 
crustations perish  sooner  by  reason  of  the  fissures  than  of  any  other 
defect,  because  the  water  imbibed  into  the  smallest  of  them,  as  well 
as  those  which  appear  on  a  cursory  view,  swells  in  the  congelation 
and  dilates  them,  and  frequent  alternations  of  wetting  and  freezing, 
gradually  widen  them,  until  the  stucco  is  bulged  and  torn  from  the 
walls.'* 

In  the  early  part  of  this  treatize,  allusion  was  made  to  the  import- 
ance of  the  acidulous  gas  being  completely  discharged  from  the  lime^ 


VARIOUS  KINDS  OF  MORTAR.  33 

to  effect  which  is  the  primary  object  in  burning  or  calcining  it,  and 
that  its  value  or  utility  depends  upon  the  method  in  which  this  opera- 
ation  is  performed ;  in  support  of  which  theorem,  a  further  reference 
will  be  made  to  the  before-mentioned  authority.  In  Section  4,  he 
says :  "On  divers  considerations  it  appeared  to  me,  that  the  perfec- 
tion of  lime  for  mortar  consists  chiefly  in  the  total  expulsion  of  the 
acidulous  gas ;  but  to  be  better  satisfied  of  this  opinion,  I  made  sever- 
al parcels  of  mortar,  the  description  of  which  will  be  abridged  by  ob- 
serving in  this  place,  concerning  all  of  them,  that  the  sand  employed 
was  coarse  Thames  sand,  and  that  the  lime  was  slaked  as  soon  as  it 
cooled  after  being  burned,  and  with  the  smallest  quantity  of  water 
necessary  for  this  purpose,  that  it  was  sifted  through  a  fine  brass- wired 
sieve  as  soon  as  it  was  fully  slaked,  and  that  each  parcel  of  mortar  was 
beaten  and  briskly  formed  with  the  quantity  of  water  which  was 
barely  sufficient  to  give  it  the  usual  consistence,  which  quantity  is  ex- 
pressed in  the  usual  term,  quan,  suff. 


Sample. 

I     Sand  3  parts 

Purest  Stone  Lime,  1 

.  part. 

2 

6  " 

it  (( 

L  ^' 

3 

3  ** 

"    Chalk   "  ] 

(( 

4 

6  " 

L  " 

5 

3  " 

Stone  Lime  as  Ob.  2,  1 

(( 

6 

6  " 

1  C( 

7 

3  " 

Chalk  Lime  as  Ob.  2,  ] 

<( 

8 

6  ** 

((  (( 

<c 

9 

3  " 

Imperfect  Limes  as  Ob.  1,  of 
best  Limestone,  ] 

tc 

10 

6  " 

U                 ((  u 

cc 

11 

3  " 

Do.       of  inferior  quality,  ] 

12 

6  *• 

il 

"Mem 

The  lime  of  Nos.  9,  10,  11  and  12  samples 

was  slaked 

whilst  it  was  hissing  hot,  in  a  covered  vessel,  because  it  would  not  slake 
sufficiently  when  it  was  suffered  to  cool  before  the  water  was  sprinkled 
on  it,  or  when  its  heat  was  soon  dissipated  by  a  free  exposure  to  the 
air,  and  hasty  evaporation  of  the  water ;  and  as  this  lime  required 


34 


VARIOUS  KINDS  OF  MORTAR. 


Beveral  hours  to  slake,  I  put  it  into  a  bottle  as  soon  as  it  was  cocl, 
and  kept  it  well  stopped  for  twenty-four  hours  before  using  it.  At  the 
same  time  I  made  two  specimens  of  mortar  with  common  chalk  lime 
and  sand  in  the  foregoing  manner. 

"  Each  specimen  or  sample  was  spread  as  soon  as  it  was  made,  to  the 
thickness  of  half  an  inch,  on  a  plain  tile  previously  soaked  in  water ; 
the  tiles  were  numbered  and  kept  close  by  each  other  in  an  airy  part 
of  my  laboratory  until  the  mortar  was  dry,  and  then  they  were  equally 
exposed,  standing  upright  in  a  place  where  the  sun  and  rain  had  free 
access  to  them. 

*'In  the  course  of  fourteen  or  fifteen  months  these  specimens 
afforded  me  a  great  deal  of  information,  which  will  be  noticed  in  due 
time ;  even  in  the  first  six  months  they  clearly  indicated  that  lime  is 
the  better  for  mortar  as  it  is  more  perfectly  freed  from  acidulous  gas. 
For  when  the  comparison  was  made  between  specimens  of  mortar 
consisting  of  the  same  quantities  of  lime  and  sand,  I  found  that  the 
mortar  made  with  well-burned  non-eifervescent  lime,  hardened  sooner 
and  to  a  much  greater  degree  than  mortar  made  with  common  lime, 
or  my  stone  or  chalk-lime  burned  in  the  manner  expressed  in  the 
second  observation  of  the  second  section ;  and  the  specimens  made 
with  the  stone  or  chalk-lime  which  was  least  burned,  were  incompara- 
bly worse  than  any  others,  for  they  never  acquired  any  considerable 
hardness,  and  they  mouldered  in  the  winter  the  sooner,  as  they  con-  » 
tained  more  of  the  lime,  and  they  also  cracked  more  in  the  drying. 
I  also  observed  that  the  specimens  which  contained  the  smaller  quan- 
tities of  well  burnt  lime  cracked  much  less  than  the  others,  or  not  at 
all ;  that  they  adhered  to  the  tiles  more  firmly,  and  were  less  injured 
by  freezing ;  but  as  the  specimens  made  with  an  excess  of  the  well- 
burnt  lime  were  no  more  cracked  than  those  made  with  equal  quanti- 
ties of  the  other  kinds  of  lime,  and  as  I  could  distinguish  the  imper- 
fections arising  from  the  excess  of  lime,  from  those  which  proceeded 
from  the  bad  quality  of  it,  I  was  satisfied  that  the  lime  which  is  most 
completely  burned  is  the  best  for  mortar. 


VARIOUS  KINDS  OF  MORTAR. 


35 


**  Considering  the  heat  which  I  found  necessary  to  extricate  the  last 
portions  of  acidulous  gas  from  chalk  or  limestone  to  be  much  greater 
than  even  adopted  in  making  lime,  so  far  as  I  had  observed  or  learnt 
from  others ;  I  suspected  that  the  lime,  commonly  in  use,  is  seldom 
or  never  sufficiently  burned. 

**0n  repeated  trials  of  several  specimens  of  such  lime,  I  found  this 
suspicion  to  be  weU-founded,  for  they  all  effervesced  and  yielded  acidu- 
lous gas,  more  or  less,  during  the  solution  of  them,  and  slaked  slowly 
in  comparison  with  well-burned  lime ;  and  in  order  to  render  the 
effervescence  conspicuous,  a  strong  acid  ought  to  be  used,  because  the 
quantity  of  water  in  a  diluted  acid  retains  a  proportional  share  of  the 
acidulous  gas,  and  a  certain  quantity  will  retain  the  whole  of  it  and 
prevent  the  eflfervescence,  because  the  effervescence  depends  on  the 
escape  of  the  elastic  fluid  out  of  the  solution.  This  is  exemplified  in 
the  mixture  of  diluted  vitriolic  acid  with  the  diluted  solution  of  salt 
of  tartar — for  these  solutions  mix  without  effervescence,  although  a 
more  concentrated  solution  of  the  alkali,  mixed  with  vitriolic  acid, 
effervesces  violently. 

"By  several  experiments  I  found  that  chalk-lime,  when  taken  as 
fresh  as  it  can  be  had  from  the  wharf,  consisting  of  pieces  which,  being 
well-burnt,  contain,  especially  in  their  central  parts,  about  one-twen- 
tieth of  their  weight  of  acidulous  gas,  of  others  which  contain  more, 
and  of  others  which  retain  near  half  their  original  quantity ;  that 
these  last  are  easily  discoverable  by  their  specific  gravity  and  hardness, 
and  that  this  is  the  part  of  our  common  lime  which  slakes  the  latest, 
and  of  the  darkest  color,  or  which  never  slakes  at  all.  On  a  peck  of 
this  lime  I  sprinkled  water,  endeavoring  to  slake  it  equally  by  throw- 
ing the  most  water  on  those  pieces  which  required  it  most.  After  the 
lime  had  stood  a  quarter  of  an  hour  to  slake,  I  sifted  it  through  a 
sieve  whose  apertures  were  one-sixteenth  of  an  inch  square,  and  then 
measuring  the  part  which  could  not  pass  through  the  sieve,  I  found  it 
to  be  one-fifth  of  a  peck,  upon  which  I  sprinkled  boiling  water,  and 
put  into  a  close  vessel,  in  a  warm  place,  to  accelerate  the  slaking  of  it. 


36 


VARIOUS  KINDS  OF  MORTAR. 


**  I  made  a  parcel  of  mortar  with  one  part  of  the  sifted  lime  and 
three  of  sand,  with  a  sufficient  quantity  of  water ;  and  another  par- 
cel with  one  part  of  the  lime,  six  of  sand,  and  the  necessary  quantity 
of  water,  and  dried  them  upon  tiles  in  the  manner  already  related,  in 
the  month  of  April,  the  weather  being  dry.  The  foregoing  coarse 
portion  of  the  lime,  after  three  hours,  was  slaked  in  several  parts  to  a 
greyish  powder,  and  I  could  perceive  that  more  of  it  would  slake  in  a 
longer  time ;  I  anticipated  this  by  reducing  the  unslaked  part  to  pow- 
der and  mixing  them  together. 

With  this  powder  and  sand  and  water  in  the  foregoing  propor- 
tions, I  made  two  specimens  of  mortar,  and  exposed  them  as  I  had 
done  the  former.  In  a  few  months  it  appeared  that  the  specimens 
last  mentioned  scarcely  deserved  the  name  of  mortar,  whilst  those 
made  with  the  first  slaked  part  of  the  lime  were  but  little  inferior  to 
the  best  specimens  made  with  the  same  proportions  of  chalk,  lime, 
and  sand. 

**  These  experiments  confirmed  me  in  my  opinion  that  lime  is  better 
for  mortar,  as  it  is  free  from  acidulous  gas ;  they  showed  one  of  the 
causes  of  the  inferiority  of  common  mortar,  and  how  to  manage  ill- 
burnt  lime  when  better  cannot  be  had. 

"Workmen  usually  slake  lime  mixed  with  sand  or  gravel  in  great 
heaps,  and  do  not*  screen  it  until  the  most  useful  part  is  debased  by 
that  which  slakes  after  five  or  six  hours  or  more,  and  which  is  little 
better  than  so  mucli  powdered  chalk.  But  if  they  would  screen  the 
lime  in  about  half  an  hour  after  the  water  is  thrown  upon  it,  the 
mortar  would  be  much  better,  although  the  quantity  of  lime  in  it 
should  be  much  less ;  for  I  observed  in  all  tlie  foregoing  specimens 
that  those  which  contained  the  smallest  quantity  of  lime  were  the 
best,  and  this  quantity  is  much  less  than  is  usually  employed  in 
mortar. 

**  These  remarks  are  applicable  to  mortar  made  with  stone-lime, 
which  is  generally  better  than  the  chalk-lime,  because  it  is  obliged  to 
be  burned  better,  as  it  will  not  slake  otherwise. 


VARIOUS  KINDS  OF  MORTAR.  37 

**In  the  brief  relation  of  these  experiments  I  have  taken  no  notice 
of  the  flinty  kernels  which  frequently  occur  in  chalk-lime,  or  of  other 
stony  masses  which  differ  from  calcareous,  and  which  are  found  in 
lime-stone,  in  order  to  avoid  being  led  into  errors. 

When  first  I  noticed  the  quantity  of  chalk-lime  which  slakes  late 
or  not  at  all,  I  suspected  that  this  difference  might  in  some  degree  be 
owing  to  the  admixture  of  argillaceous  or  other  matter,  but  on  try- 
ing these  portions  in  acids,  and  after  burning  several  specimens  of 
them,  I  was  convinced  that  the  only  impediment  to  their  slaking  con- 
sisted in  their  not  being  sufficiently  burned  in  the  kiln. " 

From  the  results  of  the  foregoing  experiments  it  is  clearly  demon- 
strated that  much  of  the  imperfection  of  mortar  is  owing  to  careless 
or  imperfect  manufacture  of  the  lime,  to  say  nothing  of  the  loss  in 
waste.  All  therefore  interested  or  concerned  in  the  building  art 
should  look  well  to  this  most  important  matter,  as  the  durability  of 
tlieir  works  depends  greatly  upon  the  character  of  the  mortar  and 
other  cementitious  substances  employed  therein. 

Before  proceeding  to  describe  the  mode  of  slaking  lime  and  prepar- 
ing mortar,  it  may  be  well  to  record  some  further  experiments  made 
by  Dr.  Iliggins,  in  reference  to  the  chemical  properties  of  lime,  and 
of  several  effects  produced  upon  lime  and  mortar  by  atmospheric  or 
other  agencies.  His  observations  upon  phlogisticated  (inflammable) 
air,  whicli  abounds  in  all  lime,  are  very  pertinent  to  our  subject,  and 
we  quote  his  words  in  Section  3  of  his  valuable  treatise,  entitled, 
"Remarks  on  the  phlogisticated  air  which  appeared  in  some  of  the 
foregoing  experiments" : — 

"As  phlogisticated  air  had  not  been  noticed  in  any  former  experi- 
ment made  on  chalk  or  lime-stone,  I  resolved  to  examine  the  elastic 
fluid  detached  from  them  in  the  usual  method.  I  extracted  several 
gallons  of  elastic  fluid  from  chalk,  during  the  solution  of  it  in  marine 
acid,  diluted  largely  with  water,  and  after  agitating  this  fluid  with 
the  necessary  quantity  of  water,  and  sometimes  with  lime-water,  until 
all  the  acidulous  gas  was  imbibed  by  them,  I  found  a  residue  consist- 


38  EXPEKIMENTS  WITH  LIME. 

ing  of  common  air,  which  was  about  one- twenty-eighth  of  the. bulk 
of  the  acidulous  gas,  in  some  trials,  in  others  it  was  much  less. 

As  I  have  not  had  time  to  examine  lime-stone  in  the  same  man- 
ner, or  to  prosecute  this  subject  by  other  experiments,  I  must  content 
myself  with  offering  a  conjecture  concerning  it. 

The  air  which  is  extracted  during  the  solution  of  chalk  seems  to 
be  that  which  chalk,  like  other  porous  bodies,  imbibes  by  capillary 
attraction,  and  it  retains  its  proper  character,  because  all  the  phlogis- 
tic matter  of  chalk  is  held  in  the  solution.  It  may  happen  likewise 
that  some  air  escapes  from  the  water  while  it  imbibes  the  acidulous 
gas,  which  it  attracts  more  forcibly ;  and  this  air  from  the  water  may 
contribute  to  the  bulk  of  that  which  appears  in  the  solution  of  cal- 
careous bodies.  But  whilst  chalk  is  deprived  of  its  acidulous  gas  by 
the  action  of  fire,  the  air  which  was  held  in  its  pores,  and  which 
attracts  phlogiston,  is  expelled  therewith,  and  consequently  in  the 
form  of  phlogistic  air.  This  conjecture  appears  the  more  proba- 
ble when  we  consider  that  the  quantity  of  air  imbibed  by  porous 
bodies  is  much  greater  than  it  appears  in  any  experiments  made  with 
the  air-pump,  as  shown  by  the  great  increase  of  weight,  which  red- 
hot  charcoal  acquires  in  cooling  in  vessels  into  which  nothing  ponder- 
able but  air  was  admitted.  The  same  attractive  powers  which  draw 
air  into  bodies,  and  then  condense  it,  resist  the  expansion  and  escape 
of  it  in  the  void,  and  detain  in  such'  a  situation  of  the  bodies  that 
quantity  whose  repulsive  powers  are  counterposed  by  the  attractive 
ones." 

Experiments  showing  how  quickly  Lime  imbibes  Acidulous 
Gas,  and  is  injured  by  Exposure  to  the  Air. 

-  "  It  was  generally  known  that  lime  exposed  to  air  loses  those  charac- 
ters which  chiefly  distinguish  it  from  whiting  or  powder  of  chalk,  and 
that  it  resumes  the  acidulous  gas  which  had  been  expelled  from  it  in 
burning.    But  being  desirous  to  know  in  what  measure  or  time  these 


EXPERIMENTS  WITH  LIME. 


39 


changes  take  place,  and  in  what  circumstances  they  are  accelerated  or 
retarded,  I  made  the  following  experiments : — 

"Exp.  1.  I  exposed  two  pounds  (avoirdupoise)  of  well-burned  non- 
effervescent  chalk  lime,  in  fragments  of  the  size  of  a  walnut,  spread 
on  a  board,  in  a  dry  unfrequented  room  ;  I  exposed  the  same  quan- 
tity of  this  lime  at  the  same  time,  and  in  the  same  manner,  in  a  pas- 
sage through  which  there  was  a  constant  current  of  air,  and  I  put  the 
same  quantity  of  this  lime,  in  fragments  of  the  same  size,  in  a  box 
which  might  hold  as  much  more  of  it,  and  placed  the  box  loosely 
covered  with  its  lid,  close  by  the  first  portion  of  the  lime. 

**In  twenty-four  hours  the  superficial  lumps  of  the  first  parcel  crack- 
ed in  some  parts  a  little,  those  of  the  second  cracked  mdre,  but  those 
of  the  third  were  not  visibly  altered.  In  forty-eight  hours  the  first 
parcel  cracked  so  much  as  to  fall  into  smaller  fragments  on  being, 
moved,  and  these  were  reducible  to  powder  by  pressing  them  between 
the  fingers ;  the  second  parcel  underwent  the  like,  or  rather  greater 
change,  for  it  was  more  cracked  and  friable ;  and  the  third  now  began 

to  crack  in  the  superficial  parts.    On  weighing  them,  I  found  the 

» 

first  parcel  weighed  two  pounds  five  ounces,  the  second,  two  pounds 
six  ounces  and  one  drachm,  and  the  third,  two  pounds  one  ounce  and 
ten  drachms ;  I  then  returned  them  to  their  former  stations. 

*'In  six  days  the  first  parcel  weighed  two  pounds  ten  ounces  and 
seven  drachms;  the  second,  two  pounds  twelve  ounces  and  one 
drachm ;  and  the  third,  two  pounds  four  ounces  and  eight  drachms. 
In  twenty-one  days,  the  first  weighed  three  pounds  and  one  drachm ; 
the  second,  three  pounds  two  ounces  and  one  drachm  and  a  half ;  and 
the  third,  two  pounds  six  ounces  and  eight  drachms.  During  this 
increase  of  weight,  the  fragments  split  into  smaller  pieces,  but  did 
not  fall  into  powder,  except  in  a  small  part  of  them,  or  when  they 
were  handled. 

"By  similar  experiments  made  on  well-burned  stone  lime,  I  found 
that  it  imbibes  matter  from  the  air  nearly  in  the  same  manner  as 
chalk  lime,  but  rather  more  slowly,  which  I  think  is  owing  to  its 


40 


EXPERIMENTS  WITH  LIME 


closer  texture ;  and  on  exposing  common  chalk  or  stone  lime  in  the 
same  way,  it  was  found  to  increase  in  weight  much  less,  and  more 
slowly. 

Exp.  2.  In  order  to  discover  the  quantity  of  water  which  the  lime 
imhibed  from  the  air,  and  which  contributed  to  this  increase  of  weight, 
I  put  each  parcel  into  a  glass  retort,  and  adjusting  to  it  my  apparatus 
whereby  all  that  is  condensed,  is  saved,  whilst  elastic  fluids  are  at 
liberty  to  escape,  I  found  that  the  quantity  of  water  contained  in  each 
parcel  of  lime  was  nearly  in  some;  and  in  others  exactly  one  twenty- 
fourth  of  the  gained  weight,  the  remainder  of  which  was  acidulous 
gas,  mixed  with  a  little  air ;  which  latter  was  not  reckoned,  having 
been  already  weighed  in  the  lime. 

If  a  glass  bottle  be  filled  with  fragments  of  well-burned  chalk  lime, 
or  stone  lime,  and  well  closed  with  a  ground  glass  stopple,  waxed 
where  it  fits  the  neck  of  the  bottle,  the  lime  will  remain  unaltered  in 
weight,  or  in  any  other  particular  for  a  year  or  two,  as  I  have  repeat- 
edly experienced  ;  even  the  phosphorescence  of  lime  is  thus  preserved 
in  its  full  lustre,  for  a  year  or  more. 

Thus  it  appeared  that  well-burned  lime  imbibes  acidulous  gas  from 
the  air,  the  sooner  as  it  is  the  more  exposed  to  it ;  that  Hme  absorbs 
this  matter  from  the  open  air,  the  more  greedily  as  it  is  the  more  per- 
fectly deprived  of  it,  previously  to  the  exposure  ;  that  lime  cannot  be 
ong  preserved  unaltered  in  any  vessels  which  are  not  perfectly  air- 
tiffht,  but  may  be  kept  uninjured  in  air-tight  vessels  filled  with  it ; 
that  chalk  lime  by  reason  of  its  sponginess,  or  by  some  other  condition 
of  it,  requires  to  be  kept  less  exposed  than  stone  lime,  and  well-burn- 
ed lime  less  exposed  than  common  lime,  to  render  the  depravation 
of  them  equal  in  equal  times ;  that  if  acidulous  gas  imbibed  in  lime 
previous  to  its  being  used  in  mortar,  be  as  injurious  to  mortar  as  the 
acidulous  gas  retained  in  an  equal  quantity  of  ill-burned  lime  is,  lime 
becomes  more  unfit  for  mortar  every  hour  that  it  is  kept  exposed  to 
air,  whether  in  a  heap,  or  in  casks  pervious  to  air.  Moreover  these 
experiments  show  that  lime  undergoes  these  changes  much  quicker 


EXPERIMENTS  WITH  LIME. 


41 


than  has  been  suspected,  since  well-burned  chalk  lime  kept  in  a  dry 
room,  imbibes  near  a  pound  of  acidulous  gas  in  three  weeks,  in  the 
summer  season. 

"  Not  trusting  to  theory,  what  I  could  prove  by  experiment^  I  did  not 
rest  satisfied  with  the  observations  and  reasons  which  might  persuade 
one,  that  lime  which  has  imbibed  some  acidulous  gas,  is  as  unfit  for 
the  uses  now  under  consideration  as  lime  which  retains  an  equal 
quantity  of  the  like  matter  by  reason  of  the  deficiency  of  heat  in 
burning  it ;  I  tried  parcels  of  well-burned  chalk  and  stone-lime,  some 
of  which  were  used  fresh,  others  exposed  two  days,  others  six  days, 
others  twenty-one  days  ;  by  making  several  specimens  of  mortar  with 
them,  and  exposing  these  specimens  in  the  manner  already  related ; 
and  in  a  few  months  I  was  satisfied  that  the  specimens  made  with 
fresh  lime  were  the  hardest  and  best,  and  that  the  others  were  worse 
as  the  lime  of  them  had  been  longer  exposed,  for  those  made  with 
the  lime  which  had  been  exposed  three  weeks,  and  had  gained  four  or 
five  ounces  to  each  pound,  were  so  easily  cut  or  broken,  so  much  effect- 
ed by  moisture  and  drying,  and  so  liable  to  break  off"  from  the  tiles, 
as  to  be  utterly  unfit  for  the  ordinary  uses  of  mortar. 

"After  this  there  remained  no  doubt  that  lime  grows  worse  for  mor- 
tar every  day  that  it  is  kept  in  the  usual  manner,  or  in  crazy  casks ; 
that  the  workmen  are  mistaken  in  thinking  that  it  is  sufficient  to  keep 
it  dry ;  that  lime  may  be  greatly  debased  without  slaking  sensibly, 
and  that  the  superficial  parts  of  any  parcel  of  lime,  which  fall  into 
fragments  or  powder  without  being  wetted,  and  merely  by  exposure 
to  air,  are  quite  unfit  for  mortar,  since  this  does  not  happen  until 
they  have  imbibed  a  great  deal  of  acidulous  gas. 

''I  now  saw  more  clearly  another  cause  of  the  imperfection  of  our 
common  cements.  The  lime  being  exposed  a  considerable  time  before 
it  is  made  into  mortar,  and  drinking  in  acidulous  gas  all  the  while, 
the  quicker  as  it  is  the  better  burned,  is  incapable  of  acting  like  good 
lime,  when  it  is  made  into  mortar,  and  often  approaches  to  the  con- 


42 


EXPERIMENTS  WITH  MORTAR. 


dition  of  whiting,  which  with  sand  and  water  makes  a  friable,  perish- 
able  mass,  however  carefully  it  be  dried. 

**In  London,  particularly,  they  use  lime  which  is  burned  at  a  dis- 
tance of  ten  or  twenty  miles  or  more,  with  an  insufficient  quantity  of 
fuel.  This  lime  remains  in  the  kiln  to  which  the  air  has  access,  for 
many  hours  after  it  is  burned  ;  it  is  then  exposed  for  some  days  in  the 
transportation  and  on  the  lime  wharves,  and  it  undergoes  further  ex- 
posure and  carriage  before  it  is  slaked  into  mortar.  It  is,  therefore, 
no  wonder  that  mortar  is  bad,  if  its  imperfection  depended  solely  upon 
the  badness  of  the  lime,  since  the  lime  is  not  only  bad  when  it  comes 
from  the  kiln,  but  becomes  worse  before  it  is  used,  and  when  slaked  is 
as  widely  different  from  good  lime  as  it  is  from  powdered  chalk." 

Experiments  and  Observations  made  to  determine  whether 
Mortar  becomes  better  for  being  kept  long  before  it  is 

USED. 

"  I  am  generally  disposed  to  think  that  there  is  some  good  reason 
for  any  practice  which  is  common  to  all  men  of  the  same  trade,  al- 
though it  may  not  be  easily  reconcilable  to  the  notions  of  others ;  and 
seeing  that  the  builders  slake  a  great  quantity  of  lime  at  once,  more 
than  they  can  use  for  some  days,  and  that  all  those  with  whom  I  con- 
versed, esteemed  mortar  to  be  the  better  for  being  long  made  before 
it  is  used,  and  that  plasterers  in  particular  follow  this  opinion  in  mak- 
ing their  fine  mortar  or  stucco  for  in-door  work ;  I  was  desirous  to 
discover  the  grounds  of  these  measures  so  repugnant  to  the  notions 
gathered  from  the  foregoing  experiments,  and  others.  I  therefore 
made  about  a  peck  of  mortar  with  one  part  of  the  freshest  and  best 
chalk  lime,  slaked,  six  parts  of  sand,  and  water  quart,  suff. ;  for  in  a 
great  number  of  experiments  I  observed  that  this  proportion  of  lime 
was  better  than  any  larger  which  I  had  tried,  or  which  the  workmen 
observe  in  making  mortar.  The  mortar  was  formed  into  an  hemi- 
spherical heap  on  the  paved  floor  of  a  damp  cellar,  where  it  remained 
untouched  twenty-four  days.    At  the  expiration  of  which  time,  it  was 


EXPERIMENTS  WITH  MORTAR.  43 


found  hardened  at  the  surface,  but  moist,  and  rather  friable  or  *  short 
than  plastic  in  the  interior  parts  of  it.  I  beat  the  whole  of  it  with  a 
little  water  to  its  former  consistence,  and  with  this  mortar  and  clean 
new  bricks,  built  a  wall  eighteen  inches  square,  and  half  a  brick  in 
thickness,  in  a  workmanlike  manner.  On  the  same  day  I  made  mor- 
tar of  the  same  kind  and  quantities  of  fresh  chalk  lime  and  sand^ 
tempered  in  the  same  manner,  and  built  a  wall  with  it,  like  the  for- 
mer, near  it,  and  equally  exposed  to  the  weather.  I  examined  the 
mortar  in  the  joints  of  these  walls  every  fortnight,  by  picking  it  with 
a  pointed  knife,  and  could  perceive  a  very  considerable  difference  in 
the  hardness  of  them,  the  mortar  which  was  used  fresh  being  invaria- 
bly the  hardest. 

"At  the  expiration  of  twelve  months,  in  pulling  these  walls  to 
pieces,  and  by  several  trials  of  the  force  necessary  to  break  the  cement 
and  separate  the  bricks,  I  found  the  mortar  which  had  been  used 
quite  fresh  to  be  harder  and  to  resist  fracture  and  the  separation  of  it 
from  the  bricks  in  a  much  greater  degree  than  the  other  experiment. 

"Considering  that  mortar  exposed  in  the  foregoing  manner  must 
imbibe  some  acidulous  gas,  though  not  so  much  perhaps  as  the  dry 
and  spongy  lumps  of  lime  drink  in  during  the  same  time ;  that  the  ad- 
ditional quantity  of  water  necessary  in  beating  it  up  the  second  time 
must  have  introduced  more  of  the  like  matter,  as  all  native  waters 
contain  some  quantities  of  it ;  that  the  fresh  exposure  in  the  last 
mentioned  agitation  of  the  mortar  must  have  contributed  something 
to  the  same  effect ;  and  lastly,  that  the  result  of  this  experiment  coin- 
cided with  the  notions  already  derived  from  others,  I  concluded  that 
mortar  grows  worse  every  hour  that  it  is  kept  before  it  is  used  in  the 
building,  and  that  we  may  reckon  as  another  cause  of  badness  of 
common  mortar,  that  the  workmen  make  too  much  at  once,  and 
falsely  imagine  that  it  is  not  the  worse,  but  better,  for  being  kept. 

Having  in  consequence  of  these  observations  had  a  great  deal  of 
conversation  with  workmen  on  this  subject,  I  could  perceive  the  origin 
of  this  error. 


44 


PLASTERERS'  LIME. 


**Some  portions  of  every  kind  of  lime  used  do  not  slake  freely,  by 
reason  of  their  not  being  sufficiently  burned,  or  by  the  admixture  of 
gypseous  or  argillaceous  matter,  and  these,  like  marl,  slake  in  time, 
though  not  so  quickly  as  the  purer  lime. 

The  plasterers,  who  use  a  finer  kind  of  mortar  made  with  lime 
and  sand,  observe  that  their  plaster  or  stucco  blisters  when  it  con- 
tains such  particles  of  unslaked  lime :  and  as  their  purpose  is  to  work 
their  stucco  to  a  smooth  surface,  and  to  secure  from  cracking,  or  any 
such  roughness  as  would  be  occasioned  by  the  slaking  or  moulding  of 
bits  of  calcareous  matter  in  the  face  of  it ;  and  as  the  hardness  of  the 
stucco  is  not  their  chief  object,  they  very  properly  keep  their  mortar  a 
considerable  time  before  they  use  it,  in  order  that  the  imperfect  pieces  of 
lime  which  passed  through  the  screen  may  have  time  to  slake  thoroughly. 

"  It  appears  that  there  is  another  reason  which  the  workmen  do  not 
notice  for  their  process,  which  is,  that  lime  imbibes  so  much  acidulous 
gas  from  the  air,  as  to  become  increased  in  bulk,  and  in  weight  be- 
yond the  half  of  its  former  quantity ;  and  as  stucco  for  inside  work, 
for  the  sake  of  a  fine  grain  and  even  surface,  must  have  a  greater 
quantity  of  lime  in  its  composition  than  is  necessary  for  cementing 
the  grains  of  sand  together,  the  incrustation  would,  by  the  access  of 
acidulous  gas  after  it  is  laid  on,  be  apt  to  swell  and  chip,  and  lose  the 
even  surface  if  the  lime  were  fresh  when  it  is  used  in  this  excessive 
quantity ;  but  this  inconvenience  is  obviated  by  their  processes,  in  which 
the  lime,  whether  slaked  into  water  or  otherwise,  imbibes  a  considerable 
quantity  of  the  gas,  and  is,  therefore,  less  apt  to  blister  and  swell, 
after  the  stucco  is  laid  on.  The  builders,  considering  the  plasterers* 
mortar  or  stucco  as  a  finer  and  better  kind  of  mortar,  think  it  not 
amiss  to  imitate  them  in  those  particulars  which  are  not  attended 
with  any  expense,  and  especially  in  the  practice  of  slaking  a  great 
deal  of  lime  at  once,  and  of  keeping  the  mortar  made  some  time  ;  and 
they  do  not  seem  to  know  that  such  mode  prevents  the  mortar  from 
ever  acquiring  that  degree  of  hardness  in  which  the  perfection  of  mor* 
tar  truly  consists.* 


PRACTICAL  INFERENCES. 


45 


Experiments  and  Observations  showing  the  Agency  or 
Acidulous  Gas  in  the  Induration  of  Mortar,  and  cir- 
cumstances WHICH  IMPEDE  OR  PROMOTE  IT.  PRACTICAL  IN- 
FERENCES. 

* '  The  observations  made  on  divers  specimens  of  mortar  at  different 
periods,  led  me  early  into  the  opinion  that  the  setting  of  mortar  de- 
pends chiefly  on  the  exsiccation  of  it,  but  that  the  induration  is  prin- 
cipally owing  to  the  accession  of  acidulous  gas  in  certain  circum- 
stances, and  not  to  the  drying,  as  the  workmen  generally  imagine.  In 
order  to  place  this  opinion  beyond  a  doubt,  and  to  discover  the  cir- 
cumstances  which  favor  or  impede  this  induration,  I  made  the  sub- 
sequent inquiries : — 

*'  Exp.  1.  I  made  mortar  with  seven  parts  of  Thames  sand,  om 
part  of  the  best  slaked  chalk-lime,  and  the  necessary  quantity  of  lime- 
water,  and  forming  a  part  of  it  into  oval  pieces,  I  put  these  into  a 
gallon  bottle,  stopped  closely  with  a  ground  glass  stopple,  waxed ;  and 
I  noted  the  gross  weight  of  the  bottle  and  mortar,  and  placed  it  ex- 
posed to  the  sun.  Having  examined  it  frequently  during  the  first 
month,  I  could  perceive  no  alteration  in  the  weight,  nor  anything 
worth  notice,  except  that  some  water  exhaled  out  of  the  mortal,  and 
condensed  in  bright  drops  on  the  sides  and  the  upper  parts  of  the 
bottle.  At  divers  times  during  six  months  afterwards,  I  shook  and 
weighed  the  bottle,  and  found  the  mortar  quite  soft,  and  the  weight 
of  the  whole  unaltered. 

"Exp.  2.  Another  portion  ot  the  same  mortar  was  spread  briskly 
as  soon  as  it  was  made,  on  oblong  pieces  of  dry  and  warm  tile,  and 
these  were  immediately  placed  over  a  sand  bath,  where  they  were 
gradually  heated  to  about  100^  Fahrenheit  for  six  hours,  and  then  to 
150°  for  two  hours  more,  when  the  mortar  was  dried  thoroughly.  1 
took  particular  notice  of  the  solidity  which  it  acquired  in  this  hasty 
dr}dng,  and  then  put  the  pieces  of  tile  with  the  adhering  mortar  into 
a  bottle,  stopped  in  the  manner  already  described,  marking  down  the 


46 


PRACTICAL  INFERENCES. 


gross  weight.  At  the  expiration  of  seven  months  the  whole  was 
found  unaltered  in  weight,  and  the  mortar  as  easily  cut  or  broken  as 
it  was  when  put  into  the  bottle. 

**ExF.  3.  Another  part  of  the  same  mortar  was  spread  whilst  fresh 
on  a  large  tile,  to  the  thickness  of  half  an  inch,  aud  the  tile  was  im- 
mediately placed  in  a  tub,  in  which  water  was  put  to  the  depth  of 
three  inches  over  the  mortar,  and  which  was  placed  in  the  open  air  to 
receive  the  rain.  At  different  periods  I  broke  the  calcareous  pellicle 
which  formed  on  the  water  and  defended  it  from  the  air  during  the 
tirst  fortnight :  afterwards  the  wind  and  rain  rendered  this  precaution 
unnecessary.  In  the  course  of  six  months,  the  mortar,  instead  of 
acquiring  any  solidity,  was  deprived  of  the  greater  part  of  its  lime 
and  what  remained  on  the  tile  was  not  much  different  from  a  layer  of 
wet  sand. 

"Exp.  4.  Another  portion  of  the  same  fresh  mortar  was  spread  on  a 
board  strewed  with  slaked  lime  to  prevent  adhesion,  and  placed  in  the 
open  air,  but  sheltered  from  the  sun.  When  this  mortar  became  suffi- 
ciently solid,  which  was  on  the  second  day,  the  pieces  were  raised, 
which  were  about  a  quarter  of  an  inch  thick,  and  placed  upright, 
fully  exposed  to  the  weather,  which  was  about  this  time  dry  and 
warm. 

**In  seven  weeks  after  this  exposure  they  were  indurated  to  a  con- 
giderable  degree.  They  resisted  a  cutting  instrument  as  much  as 
Portland  stone  does,  but  not  so  well  any  force  tending  to  break  them 
across  at  once.  I  then  placed  them  under  water  as  I  had  done  by  the 
former  portion  of  this  mortar. 

After  they  had  lain  in  water  four  months,  I  examined  them 
attentively,  and  found  them,  if  at  aU  altered,  to  be  ratTier  softened 
than  indurated  further.  I  replaced  them  in  the  water,  to  be  better 
i^tLsfied  about  them,  but  by  mistake  they  were  removed  in  my  absence 
and  lost. 

*♦  Exp.  5.  Soon  after  the  foregoing  parcel  of  mortar  was  made  I 
prepared  another  in  the  same  manner,  and  spread  a  part  of  it  on  a 


PRACTICAL  INFERENCES.  47 

tJJe  soaked  in  lime-water,  and  placed  tbe  tile  in  the  open  air,  sheltered 
from  the  sun  and  rain ;  and  after  it  had  remained  there  one  month, 
it  was  placed  where  sheltered  from  the  rain  only. 

**Exp.  6.  Another  portion  of  the  same  mortar  was  spread  fresh 
on  a  warm,  dry  tile,  which  I  placed  over  a  sand  bath  heated  to  about 
100°  Fahrenheit  for  six  hours,  and  then  to  150°  for  four  hours  more, 
at  the  expiration  of  which  it  was  solid  and  hard.  The  next  day  they 
were  placed  in  the  open  air,  exposed  to  the  sun  and  weather,  which 
was  dry  and  warm  for  a  considerable  time  afterwards. 

"  On  comparing  these  two  last  specimens  at  the  expiration  of  seven 
months,  and  again  after  six  months  more,  I  could  easily  perceive  that 
the  latter  was  inferior  to  the  former,  for  it  was  much  more  easily  cut. 
and  scaled  from  the  tile,  and  broken. 

*'Exp.  7.  With  mortar  made  the  day  after  the  former,  of  the 
same  materials  and  in  the  same  manner,  and  with  new  bricks,  which 
I  had  heated  almost  to  redness,  and  suffered  to  cool  almost  to  the 
temperature  of  my  hands,  I  briskly  erected  a  little  waU,  half  a 
brick  thick,  on  a  stone  bench  raised  for  the  purpose,  and  fully  exposed 
to  the  weather. 

**Exp.  8.  On  the  same  day,  and  with  the  like  mortar,  and  with 
cold  new  bricks  previously  soaked  in  lime-water,  I  built  another  waU 
equal  to  the  former  in  dimensions,  and  placed  it  in  same  manner  on  a 
stone  bench  in  the  open  air. 

After  nine  months,  in  puUing  these  walls  to  pieces,  and  in  divers 
comparisons  of  the  cement  of  them,  I  found  that  the  latter  cement 
adhered  better  to  the  bricks,  and  was  harder  than  the  former,  inso- 
much that  I  had  not  a  doubt  about  it. 

*'Exp.  9.  In  a  few  days  after  I  had  made  the  experiment  with  the 
warm  bricks,  I  considered  the  walls  erected  in  variable  weather,  and 
the  fence  walls  which  are  wetted  frequently  and  deeply,  while  new,  by 
rain  or  by  moisture  from  the  ground,  and  as  often  dried  as  quickly: 
and  being  desirous  to  learn  the  effects  of  such  alternations  of  wetting 
and  drying,  I  spread  mortar  made  like  those  parcels  lately  mentioned, 


48 


PRACTICAL  INFERENCES. 


on  a  large  tile  soaked  in  lime-water,  and  as  often  as  it  bad  dried  m 
fair  weather,  and  generally  at  the  interval  of  three  days.  In  the 
course  of  nine  months  I  found  it  was  much  less  indurated  than  the 
spe'cimen  made  in  the  same  manner,  and  defended  from  the  rain ;  it 
moreover  grew  green  by  means  of  a  vegetation  which  took  place  upon 
the  surface  of  it,  and  which  thrived  the  more  as  the  mortar  was  fre- 
quently wetted,  or  the  tile  longer  permitted  to  lie  flat  on  the  stone 
bench  already  mentioned. 

**I  have  often  observed  such  a  vegetation  on  mortar  which  I  had 
made  a  few  months  before,  especially  when,  in  the  summer  season, 
I  had  laid  tiles  flat  on  the  wooden  border  of  a  dust-hole,  or  when,  from 
want  of  room  to  preserve  the  specimens  in,  I  piled  many  of  them  to- 
gether in  a  damp  corner  on  the  pavement ;  I  likewise  saw  that  when 
the  vegetation  took  place,  the  induration  did  not  proceed  as  it  does 
elsewhere ;  on  the  contrary,  semi-indurated  mortar  softened  them. 

All  these  being  considered,  I  was  satisfied  that  frequent  wetting 
or  constant  moisture,  together  with  exposure  to  the  air,  injures  mortar 
to  a  great  degree,  if  it  be  not  perfectly  indurated  by  great  age  before 
it  is  exposed  to  such  trials,  and  that  the  vegetation  chiefly  depends  on 
moisture. 

"  Exp.  10.  By  the  kind  of  analysis  mentioned  in  the  10th  section, 
I  repeatedly  examined  the  proportion  of  the  acidulous  gas  to  the 
lime,  in  the  hardest  of  the  old  cements  which  I  had  collected,  and 
finding  it  in  the  best  of  them  to  be,  at  the  lowest,  in  the  proportion 
of  three  to  five,  I  rate  the  quantity  of  acidulous  gad  imbibed  by  good 
mortar,  during  the  induration  of  it,  to  be  sixty  pounds  at  least  for 
every  hundred  pounds  of  lime. 

**Exp.  11.  Such  mortar  as  that  of  the  first  experiment  of  tliis 
section,  was  formed  into  slender  pieces,  each  an  inch  broad,  a  quarter 
of  an  inch  thick,  and  three  inches  in  length.  These  were  placed  in 
an  airy  passage,  sheltered  from  the  sun  and  rain,  and  were  turned  ag 
soon  as  they  could  bear  it  without  danger  of  cracking,  ttiey  were  then 
set  upright  and  fully  exposed  on  all  sides  to  the  air.    On  the  fourth 


PRACTIC^iL  INFERENCES. 


49 


day  I  slid  four  of  the  pieces  entire  into  a  small  wide-nccked  glass  re- 
tort, which  I  set  deep  in  a  sand-bath,  with  its  nozzle  immersed  in 
quicksilver,  which  stood  cool  whilst  the  charge  was  gradually  heated ; 
in  the  course  of  forty-eight  hours,  to  about  75°  Fahrenheit,  which  is 
under  the  temperature  of  incrustations  of  this  kind  exposed  to  the 
sun  in  summer;  and  in  the  course  of  forty-eight  hours  more,  was 
slowly  heated  to  about  100°  Fahrenheit,  to  which  degree  incrustations 
are  frequently  heated  by  the  sun  in  summer.  As  the  retort  cooled, 
I  admitted  the  necessary  quantity  of  air,  and  then  left  it,  with  the 
nozzle  immersed  deeply  in  the  mercury  during  three  months.  I  then 
gently  slid  the  pieces  out  of  the  retort,  after  having  wiped  away  a  few 
drops  of  water  which  adhered  to  the  vessel  in  their  way,  and  immedi- 
ately made  the  comparison  which  I  shall  presently  mention. 

Close  to  the  retort,  and  in  a  situation  where  the  heat  was  equal  to 
that  described,  or  nearly  so,  I  placed  four  other  of  the  pieces  above 
described,  on  the  fourth  day  after  they  were  made,  and  encompassed 
them  with  sand,  but  with  a  free  access,  and  even  a  circulation  of  air  to 
them.  When  the  sand  bath  was  cooled,  I  put  these  pieces  which 
were  thus  perfectly  dried,  into  a  bottle  stopped  closely  in  the  manner 
heretofore  mentioned. 

"On  the  seventh  day  after  the  pieces  were  made,  also  on  the 
twenty-first,  and  at  the  expiration  of  three  months,  I  examined  four 
pieces  taken  from  different  quarters  of  the  remaining  parcel,  and 
found  the  quantity  of  acidulous  gas  which  they  yielded  to  correspond 
with  the  degree  of  induration,  and  the  depth  to  which  it  had  advanced 
in  them  respectively. 

"On  comparing  and  examining  the  pieces  dried  in  the  retort  and 
kept  three  months  in  it ;  the  pieces  dried  in  the  same  heat  and  freely 
exposed  to  the  air  during  four  days,  but  afterwards  kept  in  a  close 
vessel ;  and  the  pieces  which  dried  and  hardened  in  the  free  air,  with- 
out being  heated ;  I  found  that  the  first  were  friable  in  comparison 
with  the  second,  and  the  last  were  by  much  the  hardest  and  best. 

"As  the  second,  tenth,  and  eleventh  experiments,  together  with 
3 


50 


PRACTICAL  INFERENCES. 


observations  formerly  made,  show  that  the  induration  peculiar  tc 
mortar  is  not  caused  by  exsiccation ;  that  it  is  greater  as  the  calcare- 
ous matter  of  cements  approaches  nearer  to  be  saturated  with  acidu« 
lous  gas ;  that  it  is  retarded  or  prevented  as  the  accession  of  acidu- 
lous gas  is  interrupted  or  obviated ;  we  may  conclude  that  this  matter 
is  a  principal  agent  in  the  induration  of  calcareous  cements,  and  in- 
dispensably necessary  to  it. 

"By  observations  formerly  made,  but  especially  by  the  comparison 
of  the  fifth  and  eighth  experiments  of  this  section,  with  the  sixth  and 
seventh,  I  learned  that  hasty  drying  prevents  good  mortar  from  ever 
acquiring  the  hardness  which  it  otherwise  would  have ;  and  that  the 
more  slowly  the  proper  water  of  the  mortar  is  exhaled  or  absorbed 
from  it,  in  incrustation  or  brick-work,  the  more  perfect  will  be  the 
induration. 

*  *  By  the  first,  third,  and  ninth  experiments  of  this  section,  com- 
pared with  the  fourth,  fifth,  and  others,  and  by  observations  which 
led  me  to  make  these  experiments,  I  discovered  that  mortar  which  is 
not  sufi*ered  to  dry,  or  which  is  supplied  vsdth  moisture  as  fast  as  its 
proper  water  exhales,  does  not  harden,  or  hardens  only  to  a  small  de- 
gree by  an  accession  of  acidulous  gas. 

"  The  fourth  experiment  indicates  that  mortar,  whose  lime  has  not 
yet  imbibed  its  complement  of  acidulous  gas,  although  the  mass  be 
considerably  hardened,  is  liable  to  be  injured  by  soaking  in  water,  if 
it  be  pervious  to  water  so  freely  as  these  thin  pieces  were. 

' '  All  these  experiments  and  observations  conspire  to  point*  out  the 
circumstances  in  which  mortar  becomes  indurated  the  soonest,  and  in 
the  highest  degree,  and  operates  most  effectually  as  a  cement.  To 
this  end  it  must  be  suffered  to  dry  gently  and  set,  the  exsiccation 
must  be  effected  by  temperate  air,  and  not  accelerated  by  the  heat  of 
the  sun  or  fire.  It  must  not  be  wetted  soon  after  it  sets,  and  subse- 
quently it  ought  to  be  protected  from  wet  as  much  as  possible,  until  it 
is  completely  indurated ;  the  entry  of  acidulous  gas  must  be  prevented 
as  much  as  possible  until  the  mortar  is  finally  fixed  and  quiescent,  and 


PRACTICAL  INFERENCES. 


51 


then  it  must  be  as  freely  exposed  to  the  open  air  as  the  work  will 
admit,  in  order  to  supply  acidulous  gas,  and  enable  it  sooner  to  sus- 
tain the  trials  to  which  mortar  is  exposed  in  cementitious  buildings 
and  incrustations. 

''From  these  considerations  we  learn  other  causes  besides  those  al- 
ready mentioned  of  the  speedy  ruin  of  our  modern  buildings. 

''The  mortar  made  with  bad  lime  and  a  great  excess  of  it,  and 
debased  in  watering  and  long  exposure,  is  used  with  dry  bricks,  and 
not  unusually  with  warm  ones.  These  immediately  imbibe  or  dissi- 
pate the  water  and  not  only  induce  the  defect  above  noticed,  but,  as 
the  cement  approaches  nearer  to  dry,  whilst  it  is  liable  to  be  disturbed 
by  the  percussions  of  the  workmen,  render  it  more  nearly  equivalent 
to  a  mixture  of  sand  and  powdered  chalk. 

"But  in  order  to  make  strong  work,  the  bricks  ought  to  be  soaked 
in  lime-water,  and  freed  from  dust,  which  in  common  bricklaying, 
intercedes  between  the  brick  and  mortar  in  many  parts.  By  this 
method  the  bricks  would  be  rendered  closer  and  harder  ;  the  cement,  by 
setting  slowly  would  admit  the  motion  which  the  bricks  receive  when 
the  workman  dresses  them  without  being  impaired,  and  it  would  ad- 
here and  indurate  more  perfectly.  The  same  advantages  would  attend 
the  soaking  of  bibulous  stones  in  lime-water,  and  the  use  of  grouts, 
provided  this  were  made  with  good  lime,  sand  and  lime-water. 

"In  plastering,  the  workmen  always  brush  away  the  dust,  and  wet 
the  wall  on  which  they  are  to  lay  the  cement,  because  it  will  not 
otherwise  adhere.  From  what  has  already  been  said,  it  is  manifest 
that  this  ought  to  be  done  with  lime-water,  and  repeated  as  long  as 
the  wall  is  thirsty. 

"To  perceive  more  clearly  how  much  our  slight  buildings  are 
weakened  by  the  agitations  and  percussions  to  which  they  are  exposed, 
first  in  erecting  the  walls,  and  setting  the  timbers,  and  then  driving 
those  wedges  (plugs)  to  which  they  fasten  the  wainscot,  cornices  and 
other  ornaments,  we  must  observe  that  the  accession  of  acidulous  gas 
to  mortar,  was  found  to  contribute  nothing  to  the  strength  of  it. 


52 


EXPERIMENTS  ON  OLD  CEMENTS. 


when  it  entered  the  composition  before  it  was  finally  fixed  in  a  quies- 
cent state,  and  a  little  experience  is  sufficient  to  teach  us,  that  the 
same  matter  which  assists  in  the  induration  of  mortar,  never  serves 
to  repair  the  fissm'es,  or  solution  of  continuity  between  the  bricks  and 
cement  which  happen  after  it  is  set.  When  mortar  is  set,  and  before 
it  is  indurated,  it  may  easily  be  severed  from  the  bricks  and  crumbled, 
and  for  want  of  softness  it  cannot  bend  into  the  fissures,  or  resume  its 
former  condition  in  any  time.  Therefore,  by  heavy  blows,  and  in 
wedging,  our  walls  must  be  greatly  weakened,  and  the  more,  as  the 
houses  are  slight,  quickly  built  and  slightly  finished." 

jtfXPERIMENTS    ON  OlD  CeMENTS,  AUTHORISING   THE  PROPORTION 
LATELY  RECOMMENDED  OF  LIME  AND  SAND. 

To  discover  the  quantity  of  lime  and  sand  originally  used  in  many 
hard  and  old  cements,  which  was  found  by  a  previous  analysis  to  con- 
sist of  lime,  and  sand  or  clear  gravel,  I  break  a  pound  of  it  into 
small  fragments,  but  not  into  powder,  and  with  diluted  warm  acid  I 
dissolve  and  wash  away  the  calcareous  part  from  the  gravel  or  sand. 
I  measure  the  acidulous  gas  obtainable  during  the  solution,  and  know- 
ing the  weight  of  any  quantity  of  it,  in  any  temperature  or  weight  of 
the  atmosphere,  I  substract  this  weight  of  acidulous  gas  and  that  of 
the  sand  or  gravel,  from  the  whole  weight  of  the  mortar,  and  state  the 
residuary  weight  as  that  of  the  lime  originally  employed,  knowing 
that  it  could  not  have  made  so  hard  a  cement,  if  it  had  not  been  so 
far  burned  as  to  retain  very  little  acidulous  gas.  I  did  not  adopt  this 
method  of  examination  before  I  found  it  to  exhibit  the  lime  and  sand 
of  my  oldest  and  hardest  cements,  in  the  same  proportions  in  which  I 
had  mixed  them. 

"By  this  kind  of  analysis,  and  by  other  trials,  I  found  that  the 
quantity  of  lime  in  old  cements  made  with  clear,  sharp  sand,  and 
noted  for  their  hardness,  was  much  less  than  is  now  commonly  used  in 
mortar,  and  that  in  the  hardest  of  them,  it  was  very  near  to  that 


EXPERIMENTS  ON  OLD  CEMENTS. 


53 


wMch  my  experiments  indicated  to  be  the  best.  By  sharp  sand  I 
mean  those  whose  grains  are  bounded  by  flat  surfaces.  Thus  I  found 
the  inferences  made  from  my  compositions  to  be  authenticated  by 
long  experience  so  far  as  they  related  to  the  proportion  of  lime  and 
such  sand." 

The  foregoing  practical  experiments  of  Dr.  Higgins,  undoubtedly 
prove,  1st.  That  the  value  or  quality  of  lime  for  mortar  depends  upon 
its  freedom  from  acidulous  gas  ;  2d.  That  it  should  be  well  or  perfectly 
burnt ;  3d.  That  it  should  be  used  immediately  after  it  is  burned  ; 
4th.  That  its  quality  is  greatly  debased  or  deteriorated  by  exposure  to 
the  atmosphere ;  5th.  That  the  nature  or  quality  of  the  sand  employ- 
ed is  important  in  the  composition  of  mortar,  and  that  when  used 
should  be  perfectly  clean  and  free  from  any  foreign  or  objectionable 
matter ;  6th.  That  sand  of  a  mixed  size  or  gauge  is  preferable  for 
general  purposes;  7th.  That  sea  sand,  or  any  other  sand  which  con- 
tains saline  impregnations,  is  objectionable  for  mortar;  8th.  That 
the  best  proportion  of  lime  to  sharp,  clear  sand,  where  strength  and 
durability  are  concerned,  is  that  of  one  part  of  lime  to  six  or  seven  of 
sand ;  9th.  That  the  water  used  to  amalgamate  the  other  ingredients 
of  mortar  should  be  pure :  sea  or  any  salt  water,  or  any  that  are  im- 
pregnated with  mineral  or  chemical  proportions  are  not  only  objection- 
able but  injurious ;  10th.  That  as  little  water  as  possible  should  be 
used  in  the  preparation  of  mortar,  and  that  an  excess  thereof,  and 
especially  a  second  application,  after  the  mortar  has  been  once  pro- 
perly made,  is  debasing  to  the  mortar,  as  it  dissipates  the  cementitious 
properties  of  the  lime,  and  leaves  a  large  residuum  of  acidulous  gas, 
which  is  imbibed  or  absorbed  by  the  lime ;  11th.  That  lime-water  is 
far  preferable  to  crude  water  for  making  mortar,  as  the  solution  of 
lime  has  the  effect  of  disengaging  or  discharging  the  acidulous  gaa 
from  the  water ;  12th.  That  the  perfect  induration  of  mortar  depends 
upon  a  moderate  temperature  and  a  protection  from  rain,  frosts,  &c., 
and  that  (coeteris  paribus)  those  mortars  are  the  hardest  and  most 
durable  that  require  the  longer  time  to  dry ;  13th.  That  the  bricks 


54 


EXPERIMENTS  ON  OLD  CEMENTS. 


should  never  be  used  when  warm,  and  that  they  be  free  from  dust, 
never  used  in  a  dry  state,  but  should  be  previously  wetted  or  soaked 
with  water,  lime-water  being  preferable ;  14th.  That  brick  or  stone 
work  when  once  laid,  should  be  disturbed  as  Httle  as  possible,  for  when 
a  joint  of  mortar  is  broken,  after  it  is  once  set,  it  becomes  very  prob- 
lematical whether  it  will  ever  properly  unite  again. 

Having  now  described  the  several  ingredients  forming  the  composi- 
tion of  mortar,  and  exhibited  sundry  experiments  thereon,  with  their 
results  and  inferences,  from  the  inquiries  and  labors  of  the  celebrated 
Dr.  Higgins,  whose  work  and  reputation  upon  this,  stand  preeminently 
and  deservedly  high,  and  who  ranks  as  one  of  the  chief  authorities 
upon  the  subject,  we  shall  in  due  course  proceed  to  lay  before  the  in- 
quiring reader,  the  mode  of  preparing  the  several  ingredients  of  mor- 
tar, their  combination  and  application,  interspersing  our  remarks 
with  the  opinions  and  practice  of  other  professional  men  of  note,  who 
have  recorded  the  issue  of  their  labors  for  the  benefit  of  the  present  and 
future  generations ;  after  which,  we  purpose  to  complete  our  notice  of 
other  experiments  of  Dr.  Higgins  upon  the  eifects  of  combining  sundry 
foreign  matters  in  the  composition  of  mortar  or  cements  for  particular 
purposes,  to  which  will  be  appended  some  account  of  the  cements  used 
by  the  ancients ;  also  an  account  of  hydraulic  cements,  their  nature, 
properties,  use,  combination  and  application,  together  with  the  experi- 
ence, opinions,  and  experiments  of  some  of  the  first  authorities  there- 
on ;  and  the  whole  to  conclude  with  a  detailed  account  of  the 
lime-kiln,  and  various  modern  methods  of  burning  or  preparing 
lime,  fee- 
Such  being  the  ' '  programme"  of  the  entertainment  now  contemplat- 
ed, we  will  proceed  to  perform  the  several  "parts"  in  their  consecutive 
order,  trusting  the    finale"  will  be  satisfactory. 


PREPARATION  OF  COMMON  MORTAR.  55 


On  the  Preparation  of  Common  Mortas. 

The  Lime  when  perfectly  prepared  or  burnt  in  the  kiln  should  be 
speedily  withdrawn,  and  packed  for  transportation  to  its  intended  des- 
tination, in  sound  casks  or  air-tight  vessels  well  closed  down,  and 
should  be  kept  entirely  free  from  all  moisture ;  and  when  received  by 
the  builder  should  be  deposited  until  required  for  use  (which  should  be 
as  early  as  possible)  in  a  shed  or  other  dry  building,  or  if  left  out  of 
doors  should  be  closely  covered  with  a  tarpaulin,  or  boards,  and  each 
cask  should  be  unheaded  or  opened  only  as  required. 

Lime  in  this  state  is  termed  caustic  or  quick  lime,  and  in  order  to 
make  it  fit  to  be  incorporated  with  the  other  ingredients  it  must  be 
reduced  to  *^  hydrate,"  a  change  which  is  effected  by  the  application 
of  water,  which  process  is  termed  '  slaking"  and  after  which  opera^ 
tion  the  lime  is  called  slaked  lime.  Of  this  operation,  there  are  three 
methods  in  use.  The  1st.  and  most  usual  is  by  pouring  or  throwing 
the  necessary  quantity  of  water  over  the  lime  after  it  is  spread  out  into 
a  shallow  heap,  surrounded  by  the  whole  or  a  portion  of  the  sand  with 
which  it  is  to  be  incorporated.  2dly.  By  immersion,  or  plunging  the 
lime  when  deposited  in  a  basket  or  other  suitable  receptacle  for  a  few 
moments  into  water  until  the  surface  lime  begins  to  effervesce  or  boil 
and  then  turned  out  into  heaps  to  afford  time  and  opportunity  for  the 
slaking  to  be  completed.  And  3dly.,  by  mere  exposure  to  the  atmo^ 
sphere,  the  lumps  of  lime  having  been  previously  broken  up  to  about  the 
size  of  a  pigeon's  egg,  or  somewhat  smaller,  so  as  to  secure  a  more 
speedy  and  effectual  calcination  of  the  whole,  but  this  operation  must 
not  be  performed  in  wet  weather,  nor  in  too  damp  an  atmosphere ;  it 
must  be  carefully  watched,  and  so  soon  as  the  slaking  is  complete,  the 
quick  lime  must  be  immediately  used  or  deposited  in  close  casks  till 
required.  This  method  is  seldom  adopted  except  for  plasterers,  who 
consider  lime  so  prepared  preferable  for  their  work,  as  it  is  said  to 
make  the  lime  stronger.  This  mode  suits  fat  limes  (such  as  slake 
freely)  better  than  poor  limes.  Lime  slaked  by  the  second  process  will 


56  PKEPAKATION  OF  COMMON  MORTAR. 


keep  well  for  months  in  a  dry,  sheltered  spot.  But  in  every  case  where 
water  is  employed  for  slaking  lime  or  mixing  the  mortar  subsequently, 
care  must  be  taken  not  to  drown"  the  lime  for  the  reasons  before 
explained,  and  also  not  to  go  to  the  opposite  extreme,  but  to  put  the 
quantum  su ff.  at  once,  which  is  usually  computed  at  about  one  and  a 
quarter  of  the  weight  of  the  lime,  or  from  four  to  five  gallons  to  a 
cubic  foot  of  lime,  which  weighs  upon  an  average  from  28  lb.  to  35  lb., 
for  if  the  water  be  applied  tardily  or  sparingly,  the  lime  will  be  be- 
numbed, or  imperfectly  calcined,  and  gritty. 

But  the  exact  quantity  of  water  required  will  be  proportionate  to 
the  nature  and  quality  of  the  lime — ^the  fat  or  richer  sorts  will  require 
or  absorb  more  than  the  lean  or  poorer  sorts,  so  that  in  this  matter 
no  absolute  or  definite  rule  can  be  laid  down,  but  the  architect  or 
builder  must  exercise  his  observation  and  judgment — always  bearing 
in  mind  that  it  is  most  essential  that  mortar  should  be  used  fresh, 
that  it  will  consequently  be  necessary  to  apply  a  sufficiency  of  water 
at  once,  so  as  not  to  expose  the  lime  unnecessarily  long  to  the  atmos- 
phere. 

Limes  become  effete  (difficult  to  slake)  after  much  exposure  to  the 
air,  so  that  speedy  calcination  is  important  to  their  subsequent  use 
or  value. 

Limes,  when  slaked,  increase  considerably  in  bulk  and  weight  by 
their  absorption  of  both  moisture  and  air,  as  hath  before  been  alluded 
to,  and  which  increase  varies  in  different  specimens  of  lime. 

The  slaked  lime  must  be  passed  through  a  seive  or  screen,  the 
meshes  or  orifices  of  which  should  be  small,  not  exceeding  one  hun- 
dredth part  of  an  inch,  so  as  to  give  passage  only  to  the  powdry  par- 
ticles of  the  lime  or  that  which  is  perfectly  calcined,  leaving  all  the 
core  or  indissoluble  portions  of  the  lime  behind,  which  must  be  thrown 
out ;  and  if,  after  a  further  addition  of  water  and  lime,  it  should 
prove  obdurate,  and  will  not  slake,  it  must  be  abandoned  altogether ; 
however,  this  refuse  will  be  found  serviceable  to  use  in  concrete,  or  to 
fill  round  the  sides  of  walls,  piers,  drains,  &c.,  or  to  lay  under  floor 


PREPAKxVTION  OF  COMMON  MOETAR.  r,7 

next  the  earth,  where  it  would  check  damps  by  partially  absorbing 
any  rising  moisture.  The  operation  of  screening  the  lime  is  some- 
times performed  before  its  admixture  with  the  sand,  and  at  other 
times  with  it ;  of  these  two  methods  we  prefer  the  latter  for  the  fol- 
lowing reasons,  viz. :  because  it  eifects  a  saving,  of  time,  and  because 
it  insures  a  better  and  more  equable  amalgamation  of  the  ingredients, 
and  because  the  lime  is  thereby  not  so  much  exposed  to  injury  from 
the  atmosphere. 

Upon  the  perfect  completion  of  the  above-described  operation,  th« 
combined  mass  should  be  spread  out  in  the  form  of  a  hollow  cone, 
and  the  final  complement  of  the  aqueous  fluid  should  be  speedily  but 
uniformly  added ;  the  whole  mass  being  at  the  same  time  effectually 
stirred  up  and  about,  to  promote  a  proper  combination  thereof ;  oi 
what  is  better,  the  mass  should,  so  soon  as  it  is  brought  to  a  proper 
consistency,  be  passed  through  a  "pug  mill,"  which  is  a  machine 
well  known,  and  employed  in  the  preparation  of  clay  for  the  manu- 
facture of  bricks ;  but  where  this  desideratum  cannot  be  obtained,  it 
should  be  well-tempered  with  wooden  beaters,  and  also  well-turned 
over  and  incorporated  together,  as  it  is  also  very  important  for  the 
solidity  of  the  work  for  which  it  is  to  be  used,  that  the  mortar  be  well 
mixed  and  quite  unifbrm  throughout. 

Mortar  should  be  prepared  of  a  medium  consistency,  not  too  tough, " 
that  is,  not  too  dry,  nor  yet  too  short,"  that  is,  not  too  wet — for  in  the 
former  case  the  beds  and  joints  will  be  rigid  and  difficult  to  regu- 
late, from  the  absence  of  sufficient  moisture,  and  what  there  is  will 
be  speedily  absorbed  by  the  brick  or  stone,  and  the  mortar  will  indu- 
rate too  speedily,  and  in  the  latter  case,  the  joints  will  settle  too  much, 
and  the  quality  of  the  mortar  be  deteriorated. 

The  induration  of  mortar  is  dependent  upon  its  due  absorption  of 
carbonic  acid  gas  from  the  atmosphere,  and  it  is  necessary  in  order  to 
effect  the  re-union  of  carbonic  acid  with  the  lime,  that  the  latter 
should  have  received,  previously,  not  less  than  one-third  its  weight  of 
water,  and  which  is  proved  by  the  fact  that  if  dry-slaked  lime  be  put 


58  PREPARATION  OF  COMMON  MORTAR- 


into  a  jar  or  vessel  of  carbonic  acid  alone,  there  will  be  no  absorption 
whatever. 

Mortar^  stuccoes,  or  cements,  prepared  from  ill-burnt  lime,  con- 
tinue soft  and  dusty  for  a  long  time  after  being  made;  whereas,  when 
they  are  compounded  of  well-burnt  and  slaked  lime,  they  readily  im- 
bibe the  carbonic  acid  and  soon  become  thoroughly  indurated. 

Rich  limes  emit  a  strong  hissing  noise  and  great  heat  during  the 
process  of  slaking,  but  the  poor  or  meager  limes,  which  nevertheless 
are  the  most  valuable,  undergo  the  operation  with  less  apparent  ex- 
citement; and  in  proportion  to  the  extraneous  or  foreign  matter 
wliich  they  contain,  and  with  some  varieties  of  hydraulic  limes,  no 
visible  effect  will  be  observable  in  them  until  after  the  lapse  of  several 
hours. 

The  purest  limes  require  the  largest  proportion  of  sand,  and  require 
the  most  water  in  slaking,  and  harden  in  less  time  than  the  common 
limes. 

Hydrate  of  lime,  or  the  powdered  state  of  lime  produced  by  slaking 
whilst  in  a  damp  state,  soon  faUs  away  and  is  dissolved  in  water,  and 
the  same  result  is  produced  by  alumina,  manganeze,  silica,  &c.,  but 
not  to  so  great  an  extent. 

In  the  before-mentioned  experiments.  Dr.  Higgins  determined  that 
the  best  proportion  of  lime  and  sand  is  one  measure  of  the  former 
to  six  or  seven  of  the  latter ;  but  in  England  the  tradesmen  usually 
combine  one  hundred  and  a  half,  that  is,  150  pecks,  or  37/^  striked 
bushels  of  chalk-lime  with  two  loads  of  sand,  that  is,  60  bushels  of 
sand ;  and  with  the  like  quantity  of  stone  lime  they  usually  put  two 
and  a  half  loads  of  sand,  or  75  bushels,  which  are  very  erroneous 
proportions,  as  the  sand  experiments  clearly  show,  and  as  our  own 
experience  has  often  testified. 

The  above-mentioned  quantities  are  each  sufficient  to  do  a  rod  of 
brick-work,  which  is  equal  to  212%  feet  of  one  and  a  half  brick  thick, 
or  408/^  feet  of  one  brick  thick ;  to  this  standard  the  calculation  of 
all  brick- work,  of  whatever  thickness  it  may  be,  is  reduced,  and  by 


EXPERIMENTS  AND  RESULTS,  59 

fthis,  the  architect,  in  his  specification  of  works,  usually  limits  or  de- 
termines  the  quantity  of  lime  and  sand  to  be  used. 

Various  substances  are  sometimes  added  to  mortar  to  increase  the 
tenacity,  and  they  impart  thereto  the  principles  of  hydraulic  cements 
to  a  greater  or  lesser  degree. 

These  chiefly  consist  of  burnt  clay,  ashes,  scorisB,  iron  scales  and 
filings,  pulverized  broken  potter's  ware,  bricks,  tiles,  &c.,  all  of  which 
are  very  useful  for  mixing  with  lime  or  mortar  to  increase  their  hard- 
ness, but  these  must  be  veiy  pure  and  dry,  and  reduced  to  a  fine 
powder  before  being  mixed  with  the  lime.  To  enable  lime  to  harden 
by  the  absorption  of  carbonic  acid,  it  must  be  divided  as  minutely  as 
possible  so  as  freely  to  admit  the  air,  and  for  which  purpose  these  sub- 
stances are  available.  Any  of  these  compositions  are  very  useful  for 
the  purpose  of  bedding,  chain-bond,  wall-plates,  templates,  common 
bond  or  bearers  upon  walls,  instead  of  lime  mortar,  the  properties  of 
which  are  highly  injurious  to  wood,  and  on  that  account  ought  never 
to  be  brought  into  close  contact  therewith. 

Common  mortar  of  ashes  is  prepared  by  mixing  two  parts  of  fresh 
slaked  lime  with  three  parts  of  wood  ashes  together,  and  when  cold, 
to  be  well  beaten,  in  which  state  it  is  usually  kept  for  a  considerable 
time ;  and  if  beaten  two  or  three  times  previous  to  using  it,  will  be 
found  to  improve  by  keeping.  In  resisting  the  alternate  effects  of 
moisture  and  dryness,  this  mixture  is  by  some  persons  thought  to  be 
superior  to  terras  mortar,  but  not  nearly  equal  to  it  when  applied  quite 
under  water. 

We  will  now  proceed  to  quote  further  from  Dr.  Higgin's  work; — 

ExPERmENTS    SHOWING    THE    EFFECTS    OF     FiNEST    SaND  AND 

QuARTOZE  Powder  in  Mortar  ;  Observations  on  the  finest 
Calcareous  Cements  ;  Practical  Precepts. 

**The  last-mentioned  notion  led  me  to  suspect,  soon  after  the  fore- 
going  experiments  were  made^  that  although  the  fine  Thames  sand 


60 


EXPERIMENTS  AND  RESULTS. 


made  better  mortar  than  the  coarse  sand  or  rubble  afforded,  the 
mortar  will  not  always  be  the  better  as  the  sand  is  finer,  however 
sharp  it  may  be.  I  therefore  procured  a  large  quantity  of  the  very 
fine  pit  sand,  used  in  London  under  the  name  of  "house  sand."  I 
washed  away  the  clay  with  which  it  abounds,  and  dried  it.  Viewing 
it  when  thus  cleansed,  with  a  lens,  I  estimated  the  size  of  the  grains 
to  be,  at  a  medium,  about  one-ninth  of  that  of  any  fine  Thames  sand ; 
this  I  shall  call,  finest  sand.  At  the  same  time  I  was  favored  by  Mr. 
Bentley,  the  ingenious  manufacturer  of  ornamental  Staffordshire 
ware,  with  the  necessary  quantity  of  the  fine  powder  of  calcined  flints, 
which  is  prepared  for  his  manufactory.  With  divers  mixtures  of  these 
with  lime-water  and  lime,  in  a  variety  of  proportions,  and  with  each 
and  both  of  these  ingredients  blended  with  coarse  and  fine  sand,  lime, 
and  lime-water  in  similar  proportions,  I  made  a  great  number  of 
specimens  of  mortar,  which  I  tried  in  the  manner  already  described ; 
and  noting  my  observations  on  them  I  found  the  following  to  be  the 
most  eligible,  for  the  concise  recital  intended  in  this  essay  : — 

*'lst.  Mortar  containing  the  quantity  of  lime  necessary  to  the  plas- 
ticity and  other  desirable  properties  of  it,  or  a  greater  quantity  of 
lime,  is  the  more  liable  to  crack  in  drying,  as  the  sand  of  it  is  finer. 

Mortar  made  with  this  finest  sand  and  lime,  does  not  grow  so 
hard,  or  resist  fracture  so  forcibly,  as  that  made  with  the  fine  Thames 
6and  and  lime,  in  the  same  proportions,  or  any  others  nearest  to  these. 
But  the  former  mortar,  when  composed  of  about  six  parts  of  sand, 
one  of  lime,  and  the  necessary  quantity  of  lime-water,  and  slowly 
dried,  becomes  much  harder  than  many  of  the  calcareous  stuccoes  com- 
monly used  by  the  plasterers. 

"3d.  Mortar  composed  of  lime,  fine  Thames  sand,  and  the  finest 
sand,  is  worse  as  the  quantity  of  the  finest  sand  is  greater,  and  this 
holds  true  in  every  tried  proportion  of  the  sands  and  lime. 

"4:th.  Mortar  consisting  of  lime,  coarse  Thames  sand,  fine  Thames 
sand,  and  finest  sand,  is  the  worse  as  the  quantity  of  the  latter  ia 
greater,  when  the  comparison  is  made  between  it  and  the  cement 


EXPERIMENTS  AND  RESULTS. 


61 


made  with  the  same  quantities  of  lime,  and  the  best  mixture  of  coarse 
and  fine  Thames  sand. 

**5th.  Mortar  made  with  flint  powder,  lime,  and  lime-water,  in 
any  proportion,  is  more  liable  to  crack  in  drying,  than  mortar  com- 
posed of  any  sand  and  lime ;  it  is  moreover  incapable  of  hardening  to 
so  great  a  degree,  whether  it  be  tested  by  a  chisel,  or  by  breaking  it 
across.  But  mortar  made  with  about  five  parts  of  flint  powder,  one 
of  lime,  and  the  necessary  quantity  of  lime-water,  is  neverthelcLb  pre- 
ferable to  any  stucco  now  used  for  inside  work,  for  the  finishing  coat, 
because  it  has  a  more  lively  whiteness,  and  assumes  a  finer  surface, 
which  I  think  might  be  made  to  imitate  that  of  marble ;  it  requires, 
however,  to  be  dried  very  slowly. 

"6th.  Mortar  made  with  coarse  Thames  sand,  fine  Thames  sand, 
flint  powder  and  lime,  or  with  fine  Thames  sand,  finest  sand,  flint 
powder,  and  lime,  or  with  the  finest  sand,  flint  powder  and  lime,  is 
worse  as  the  quantity  of  flint  powder  is  greater,  relatively  to  that  of 
the  sand. 

"  Upon  the  whole  it  appeared,  that  the  finest  sand  is  injurious  in 
mortar  which  is  exposed  to  the  weather,  and  that  flint  powder  is  still 
worse,  but  that  this  last  may  be  advantageously  used  in  composing 
stucco  for  inside  work,  in  which  a  fine  texture,  pleasing  color,  and 
smooth  surface  are  preferred  before  extreme  hardness,  and  in  which 
the  drying  may  be  regulated  so  as  to  prevent  the  incrustation  from 
cracking. 

"  Instead  of  resting  satisfied  with  the  bare  discovery  of  the  fact,  that 
very  fine  sand  or  quartoze  powder  is  incapable  of  making  so  good  a 
cement  as  may  be  formed  with  coarser  sand,  although  fine  Thames 
sand  and  lime  make  a  better  cement  than  can  be  composed  with  the 
coarse  sand  and  lime,  and  that  the  mixture  of  the  very  fine  sand,  or 
siliceous  powder,  with  the  Thames  sand,  is  rather  injurious  than  use- 
ful, although  the  mixture  of  the  coarse  Thames  sand  with  the  finer,  is 
better  for  mortar,  than  either  of  them,  unmixed.  I  took  a  great  deal 
of  pains  to  learn  the  cause  of  this,  in  order  to  confirm  or  correct  the 


62  EXPERIMENTS  AND  RESULTS. 


foregoing  notions,  and  render  the  precepts  which  flow  from  this  fact, 
the  more  satisfactory. 

*'By  sorting  my  finest  sand  into  divers  parcels,  in  sifting  it  through 
different  sieves,  by  measuring  the  meshes  of  these,  and  by  viewing  the 
grains  of  each  parcel  ranked  closely  on  a  scale,  I  perceived,  more 
clearly  than  I  had  done  before,  the  roundness  of  this  sand ;  I  more- 
over found  that  the  grains  of  the  coarsest  parcel  were,  at  a  medium 
of  their  respective  bulks,  upwards  of  sixteen  times  larger  than  those 
of  the  finest  parcel ;  the  grains  of  the  other  parcels  being  of  divers  in- 
termediate sizes.  As  this  sand  therefore  has  every  advantage  attain- 
able by  the  admixture  of  coarse  and  fine  grains,  and  every  disadvan- 
tage resulting  from  the  smallness  and  roundness  of  its  grains,  I 
learned  the  reason  why  the  defects  attending  such  fine  round  sand 
in  mortar  are  not  corrected  by  any  mixture  of  coarse  sand.  How 
these  defects  are  induced  by  the  finest  sand  and  flint  powder,  we  may 
conceive  in  the  following  manner : — 

Having  already  shown  how  the  roundness  of  sand  tends  to  render 
the  mortar  made  with  it  defective,  I  may,  without  any  further  illus- 
tration of  this  matter,  reckon  on  this  figure  of  the  grains  of  finest 
sand,  as  one  cause  of  the  imperfection  of  the  mortar  in  which  it  is 
used. 

"  There  is  nothing  to  prevent  the  laminas  of  lime-paste,  which  inter- 
cede the  grains  of  finest  sand,  from  being  as  thick,  in  the  mass  of 
mortar  made  with  it,  as  they  are  in  mortar  made  with  coarse  sand, 
but  they  are  likely  to  be  thicker  in  general,  as  the  faces  of  the  finer 
grains  are  rounder. 

The  number  and  extent,  moreover,  of  these  laminae,  must  be 
greater,  in  the  sum,  in  the  finest  sand,  than  in  the  coarser,  and  it  is 
for  these  reasons  that  more  lime-paste  is  required  to  make  mortar 
with  the  former  than  the  latter,  since  the  mortar  is  not  formed  until 
the  paste  developes  every  grain  and  fills  the  interstices.  In  this  view 
of  the  subject  we  discover  another  cause  of  the  defect  lately  men- 
tioned.   If  we  use  lime  with  a  sparing  hand  it  will  not  extend  be- 


EXPERIMENTS  AND  RESULTS. 


63 


tween  all  the  grains  or  fill  the  spaces ;  we  find  the  mortar  too  "short" 
whilst  fresh,  and  it  is  as  defective  in  strength  when  indurated  as  it  is 
deficient  of  the  cementing  matter.  When  we  use  the  necessary  quan- 
tity of  lime,  the  calcareous  matter  bears  a  greater  proportion  to  the 
quartoze  grains,  in  this  finest  mortar,  than  in  the  coarser,  and  this 
renders  the  former  defective,  according  to  the  principles  of  aggregation 
already  expressed. 

*' A  third  cause  of  the  imperfection  of  mortar,  made  with  finest 
sand,  or  containing  a  larger  quantity  of  it,  appears  on  the  considera^ 
tion  of  the  quantity  of  lime. 

"We  have  repeatedly  seen  that  mortar  contracts  the  more  in 
drying,  and  is  the  more  apt  to  crack,  as  it  contains  a  greater  quantity 
of  lime-paste,  and  as  the  finest  sand  requires  an  extraordinary  quan- 
tity of  the  paste  to  form  it  into  mortar,  the  aggregate  of  such  a 
cement  is  likely  to  be  impared  by  fissures,  although  they  do  not 
always  appear,  by  reason  of  their  smallness. 

"Other  causes  of  the  experienced  imperfection  of  fine  mortar 
might  be  added,  which  have  no  relation  to  the  figure  of  the  grains  of 
sand,  or  the  quantity  of  calcareous  matter,  but  to  avoid  an  excess  of 
theory,  I  forbear  to  mention  them,  and  shall  only  add  a  conjecture 
concerning  the  finer  cements. 

"When  a  cementitious  mass,  like  mortar,  is  cut  with  an  edged 
instrument  or  broken  across,  we  may  observe  that  the  fracture  happens 
in  the  shortest  line,  along  the  laminse  of  the  weaker  cementing  mat- 
ter, and  seldom  or  never  in  the  shorter  right  line  passing  through 
the  harder  grains  and  the  cement  alternately,  although  the  impressed 
force  tends  to  cause  the  solution  of  continuity  in  the  shortest  or  in  a 
right  line.  By  the  principle  of  mechanics,  the  resistance  to  such  forces 
is  greater  (coeteris  paribus)  as  the  line  of  fi^acture  is  longer,  whether 
it  be  straight  or  winding  in  any  course ;  and  it  is  for  this  reason  that 
a  wall  built  with  any  large  stones,  is  less  liable  to  crack,  although  the 
foundation  should  fail  near  one  extremity  of  it,  than  a  brick  wall  built 
with  the  same  kind  of  cement  on  the  like  ground ;  or  that  a  wall. 


64 


EXPERIMENTS  AND  RESULTS. 


whose  bricks  are  jointed  in  the  present  fashion,  is  more  secure  from 
cracking,  that  that  which  should  be  built,  on  the  like  infirm  ground, 
with  the  same  kind  of  bricks  standing  over  each  other,  not  jointed, 
but  with  their  sides  and  ends  flushed,  as  the  workmen  express  it. 

''As  cements  are  cut  and  broken  in  the  direction  of  the  cement, 
and  not  in  the  shorter  line,  as  the  cracks  in  ill-founded  walls  run 
winding  along  the  joints,  instead  of  going  in  the  shortest  course, 
through  the  bricks  and  joints  alternately,  and  the  resistance  of  such 
cementitious  masses,  estimated  by  mechanical  theory,  is  greater,  as 
the  line  of  fracture  is  necessarily  elongated,  by  the  stronger  aggrega- 
tion of  certain  parts  of  them.  I  am  inclined  to  think  that  calcareous 
cements  made  with  lime,  and  quartoze  powder  will  always  be  found 
weaker  under  trial  by  the  chisel  or  by  fracture,  as  the  quartoze  sand 
or  powder  is  finer,  because  the  line  of  fracture,  which  takes  the  course 
of  the  cementing  matter,  is  shorter,  in  any  equal  depth  of  such  masses, 
as  the  hard  quartoze  grains  are  finer  and  rounder. 

"As  flint  powder  consists  of  exceedingly  fine  grains  of  silicious 
stone  worn  to  roundness  in  the  grinding,  what  has  been  said  of  the 
finest  sand  is  sufficient  to  show  why  the  cements  which  contain  flint 
powder  are  the  worst  of  all  those  we  have  mentioned. 

''  The  customary  method  of  washing  sand,  even  for  stucco,  which  is 
to  be  exposed  to  the  weather,  consists  in  passing  it  through  a  sieve,  by 
a  circular  horizontal  motion  of  it,  in  a  tub  filled  with  water,  which 
flows  over  and  carries  away  with  it  any  light  matter  which  can  be 
long  suspended  in  water,  as  fast  as  the  sand  runs  through  the  sieve 
into  the  vessel.  But  this  process  is  inadequate  to  our  views,  because 
the  finest  sand  subsides  along  with  the  best,  and  those  in  the  precipita- 
tion entangle  and  carry  down  with  them  a  great  deal  of  finer  powder 
and  dirt.  Where  such  a  method  must  be  pursued  for  want  of  other 
utensils,  or  through  the  scarcity  of  water,  the  sand  ought  to  be  agitat- 
ed again  in  small  parcels,  with  a  part  of  the  water  which  has  cleared 
by  subsidence,  and  immediately  after  the  agitation,  the  muddy  water 
ought  to  be  poured  off"  before  the  light  parts  have  time  to  subside  in  it. 


EXPERIMENTS  AND  RESULTS. 


65 


But  the  useful  part  of  sand  is  more  effectually  freed  from  the  finer  and 
noxious  parts,  by  sifting  it  in  streaming  water,  whose  current  is  to  be 
so  managed  that  it  shall  carry  away  the  mud  and  the  sand  which  is 
too  fine,  whilst  the  better  part  subsides  in  a  proper  receptacle. 

**In  the  subsequent  pages  I  purpose  to  show  the  integrant  parts  of 
gravel,  and  their  several  properties  in  mortar ;  for  the  present  purpose 
it  will  be  sufficient  to  observe  that  the  gravel  commonly  employed  in 
building  consists  chiefly,  after  it  is  screened,  of  rubble,  coarse  sand, 
fine  sand,  and  finest  sand,  similar  to  those  used  in  our  experiments. 
This  is  obvious  on  the  bare  inspection  of  it,  and  leads  us  to  discover 
another  cause  of  the  weakness  of  our  modern  cements,  in  the  composi- 
tion of  which  no  other  precaution  is  used,  respecting  the  gravel, 
except  to  separate  the  stones  and  coarsest  rubble  from  it  by  screen- 
ing. 

**When  it  happens  that  the  screened  gravel  contains  more  than  a 
certain  quantity  of  rubble,  relatively  to  that  of  coarse  and  fine  sand, 
similar  to  those  described,  the  mortar  made  with  it,  must,  according 
to  our  experiments,  be  defective.  It  will  be  so  likewise,  whenever  the 
coarse  sand  of  it  predominates  over  the  fine  sand,  to  a  greater  degree 
than  that  which  was  found  consistent  with  the  perfection  of  mortar ; 
and  when  the  quantity  of  finest  sand  happens  to  be  considerable  in 
gravel,  the  mortar  made  with  it  must  be  faulty  in  a  greater  degree. 

"  Now  supposing  the  gravel  to  be  freed,  by  the  screening,  from 
everything  more  injurious  than  finest  sand  and  quartose  powder,  we 
perceive  that  the  artist  who  is  ignorant  of  the  advantages  of  sizing  his 
gravel,  and  uses  it  in  its  native  state,  as  chance  presents  it,  has  the 
odds  greatly  against  his  making  good  mortar,  although  he  may  some- 
times do  it,  without  knowing  the  reason,  as  we  shall  find  hereafter, 
for  his  chance  is,  that  the  native  gravel  shall  consist  of  coarse  and  fine 
sand  mixed  in  the  proportion  of  three  to  four,  or  of  the  rubble,  coarse 
and  fine  sand  mixed  in  the  proportions  above  recommended ;  and  that 
it  shall  contain  little  or  no  sand  like  our  finest  sand,  but  the  chancea 
against  him  are  as  numerous  as  there  are  other  distant  proportions  of 


66 


EXPERIMENTS  AND  RESULTS. 


rubble,  coarse  and  fine  sand  in  gravel,  and  as  the  kinds  of  gravel  used 
are,  vi^hich  contain  the  finest  sand,  or  still  finer  quartoze  grains  in 
efficient  quantities. 

'*In  great  cities  where  gravel  cannot  be  procured  so  cheap  as  tne 
rubbish  of  old  walls,  which  the  workmen  lay  in  the  streets  to  be  ground 
to  powder  by  the  passing  carriages,  they  use  this  rubbish,  screened,  in 
the  place  of  sand  or  gravel,  in  making  mortar.  It  consists  of  the 
gross  powder  of  bricks,  and  of  mortar  indurated,  as  much  as  bad  mor- 
tar can  be,  by  time,  and  some  builders  affirm  that  it  is  better  than 
sand  or  gravel  for  mortar.  It  is  certainly  eligible  when  the  price  is 
chiefly  considered,  in  any  other  view,  it  is  not  so. 

*'From  my  past  experience,  I  judged  the  calcareous  powder  of  an 
old  cement,  and  that  of  the  bricks,  to  be  a  brittle,  perishable  and  weak 
substitute  for  grains  of  sand,  and  the  quantity  of  dust  in  such  ground 
rubbish,  to  be  highly  injurious,  but  as  the  opinion  of  the  workmen  was 
against  me,  I  made  some  trials  of  it. 

"I  found  that  less  lime  was  required  to  make  fat  mortar  with  this 
ground  rubbish,  than  with  my  best  mixtures  of  sand,  which  is  no 
small  recommendation  of  it  in  certain  jobs,  and  is  owing,  in  my 
opinion,  to  the  ground  calcareous  part,  which,  so  far  as  it  is  finely 
powdered,  is  equivalent  to  whiting,  but  the  mortar  made  with  the 
rubbish  appeared,  in  every  stage  of  induration,  and  in  every  compari- 
son, except  that  of  plasticity,  to  be  greatly  inferior  to  that  made  with 
mixed  sand  and  lime  in  the  same  proportions. 

* '  If  the  workmen  would  confine  their  opinion  to  the  comparison  of 
such  rubbish  mortar,  with  that  in  which  clayey  gravel  is  used,  or  with 
the  cements  made  with  the  ashes  and  ordure  of  the  town,  dug  out  in 
preparing  foundations  of  houses,  in  those  places  which  were  formerly 
receptacles  of  such  matter,  they  might  maintain  it  on  divers  grounds 
which  will  be  examined  hereafter,  but  otherwise  it  is  erroneous."  ^ 


EXPERIMENTS  WITH  SAND,  &c. 


67 


Experiments  made  on  a  larger  scale  with  our  Best  Mix- 
ture OF  Sands,  Lime-water  and  Lime. 

**  At  a  subsequent  period,  I  repeated  a  great  number  of  the  forego- 
ing experiments,  particularly  those  which  exhibit  mortar  in  the  im- 
proved state  to  which  I  had  brought  it ;  and  finding  my  former  obser- 
vations to  be  true,  when  the  circumstances  were  not  varied,  I  resolv- 
ed to  try  my  best  cements  in  larger  quantity,  and  in  other  circumstan- 
ces. 

*'I  applied  them  in  the  way  of  stucco,  on  the  brick  walls  of  houses 
in  different  aspects,  but  chiefly  in  that  of  the  meridian  sun ;  covering 
a  square  yard  at  least  with  each  specimen,  after  I  had  repeatedly 
wetted  the  wall  with  lime-water. 

"By  these  trials  I  found  that  mortar  made  with  four  parts  of  coarse 
sand,  and  three  of  fine,  wetted  with  lime-water,  and  beaten  up  with 
one  of  my  lime,  slaked  with  lime-water,  although  it  could  be  easily 
spread  on  a  horizontal  plane,  or  used  in  building  with  bricks,  was 
rather  too  *  short'  for  plastering  on  the  perpendicular  surface  of  a  wall. 
It  might,  however,  be  laid  on  in  small  successive  portions,  by  a  dex- 
terous management  of  the  trowel,  and  especially  by  sliding  the  tool  on 
it  upwards. 

"When  the  weather  continued  temperate  and  dry  for  eight  or  ten 
days  after  the  incrustation  was  made,  and  no  great  quantity  of  rain 
fell  for  three  or  four  weeks  afterwards,  this  stucco  answered  my  ex- 
pectations, for  it  did  not  crack  in  the  least,  and  in  three  months  was 
almost  as  hard  as  Portland  stone  at  the  surface,  where  the  induration 
first  takes  place  for  the  reasons  formerly  mentioned,  but  it  was  too 
coarse  to  represent  a  fine  grained  stone. 

"Having  made  two  pieces  of  incrustation  of  this  kind,  on  the  same 
wall,  and  knowing  that  calcareous  cements  cannot  harden  so  soon  as 
necessary  in  outside  stuccoing,  unless  they  be  pervious  to  acidulous  gas 
in  which  case  they  may  drink  in  water  likewise.  I  frequently  wetted 
one  of  the  pieces,  in  about  three  months  after  it  was  formed,  with 


68 


EXPERIMENTS  WITH  SAND,  &c. 


iime-water,  expecting  that  the  calcareous  matter  of  it  would  crystal- 
lize in  the  cement,  and  render  it  harder  and  closer.  I  was  not  dis- 
appointed, for,  in  the  course  of  a  month  I  found  this  piece  of  stucco 
harder  and  closer  than  the  former,  and  at  the  surface  as  much  supe- 
rior in  these  particulars  to  Portland  stone,  as  the  other  was  inferior  to 
it.  I  have  since  found  that  lime-water  has  not  this  effect,  if  the  in- 
crustation be  wetted  with  it  before  it  is  quite  dry  and  indurated  slowly, 
to  vie  with  Portland  stone  in  that  kind  of  strength  which  is  tried  by 
grinding  Portland  stone  on  it,  or  scraping  it  with  a  chisel,  for  any 
other  trial  of  incrustations  is  unfair,  until  the  induration  has  proceeded 
equally  throughout  the  mass. 

When  the  incrustations  made  of  the  same  cement,  were  wetted 
by  rain  in  two  or  three  days,  or  sooner,  after  they  were  applied,  and 
especially  when  the  wind  blew  the  rain  forcibly  upon  them,  they  were 
sensibly  injured,  for  they  never  afterwards  looked  or  hardened  so  well 
as  the  former  specimens  of  stucco. 

**In  these  particulars  the  large  incrustations  agreed  with  those 
made  on  tiles,  but  the  same  agreement  did  not  appear  in  the  incrus- 
tations which  I  had  made  with  the  same  composition  on  a  wall  which 
fronted  the  meridian  sun,  at  a  time  when  the  weather  was  very  hot, 
for  these  showed  a  few  slender  cracks  in  the  course  of  three  days. 
When  in  the  same  situation  and  weather,  and  on  a  coarse  stucco  of 
this  kind,  I  spread  in  about  two  hours,  after  it  was  laid  on,  a  thinner 
coat  of  cement  made  with  finer  sand  in  order  to  represent  a  finer 
grained  stone,  the  incrustation  consisting  of  these  two  layers  cracked 
more  than  the  former. 

After  many  repetitions  of  these  experiments  in  the  hottest  weather 
with  the  same  result,  I  perceived  that  the  trials  of  such  cement  on 
tiles  are  not  so  severe  as  those  to  which  they  may  be  exposed  some- 
times in  incrustations  on  walls.  In  the  latter  case,  the  stucco  is  very  un- 
equal in  thickness,  for  in  the  hollow  joints  and  depressions  of  the  bricks 
it  is  near  an  inch  thick,  when  over  the  prominences  it  has  not  more 
than  one-eighth  of  this  thickness ;  and  as  it  dries  soonest  in  the  thin 


EXPERIMENTS  WITH  SAND,  &c. 


69 


parts,  the  unequal  contractioti  seems  to  be  the  cause  of  those  cracks, 
which  would  not  happen  to  the  same  cement  laid  on  the  flat  surface 
of  a  tile  ;  it  seems,  moreover,  that  such  a  composition  may  more  easily 
contract  in  drying,  without  cracking,  as  the  crust  is  made  narrower 
or  less  extensive.  But  I  impute  the  cracking  chiefly,  to  the  foregoing 
unequal  contraction,  accelerated  not  only  by  the  heat  of  the  sun  and 
the  wall,  but  by  the  thirsty  bricks,  for  if  we  form  our  judgment  accord- 
ing to  the  quicker  or  slower  progress  of  the  exsiccation,  and  the  stiff- 
ness which  the  cement  acquires  in  the  act  of  spreading  it  on  the  brick 
wall,  and  the  wetting  of  this  last,  superficially  with  lime-water,  is 
not  equivalent  to  steeping  the  tiles  for  a  few  minutes  in  the  same 
liquor. 

<'When  with  a  view  of  preventing  fissures,  I  stuccoed  a  part 
of  the  same  wall  (wetted  with  lime-water)  with  cement  containing 
the  mixed  sands  and  limes  in  the  proportion  of  fifteen  to  two,  in  the 
same  kind  of  weather,  I  found  the  difiiculty  and  waste  in  applying  it 
greater  than  in  the  former  instances,  and  that  it  was  defective  in 
strength  and  closeness  for  want  of  lime,  although  it  did  not  crack. 
When  through  distrust  of  my  former  experiments,  I  used  more 
than  one-seventh  of  lime,  the  cracks  were  still  larger  and  more  nume- 
rous. 

"To  guard  a  recent  incrustation  from  the  rain,  and  to  secure  it 
from  cracking  in  the  circumstances  last  described,  I  proposed  the  ex- 
pedient of  hanging  sail-cloth  on  the  cornices  and  scaffolding,  but  the 
expense  of  this  measure,  and  the  danger  arising  from  it  in  windy 
weather,  were  strong  objections.  Embarassed  by  this  unexpected 
difficulty,  I  resolved  to  change  my  ground,  and  try  what  might  be 
done  by  a  new  series  of  experiments,  in  which  I  intended  to  use  every 
known  cheap  substance,  whether  it  could  be  reasonably  supposed  to 
have  any  considerable  effect  towards  securing  a  recent  incrustation 
against  the  above-mentioned  impressions  of  rain  or  hot  weather,  or 
could  be  suspected  of  rendering  the  stucco  defective.  I  prosecuted  this 
Inquiry  with  great  alacrity,  because  I  was  certain  that,  although  I 


70 


EXPERIMENTS  WITH  GRAVEL. 


should  fail  in  the  attempt  towards  improvement,  I  should  learn  how 
in  future  to  avoid  those  things  which  being  naturally  blended  in  cer- 
tain kinds  of  lime-stone,  sand  or  water,  tend  to  render  the  mortar 
made  with  them,  faulty.  I  had  already  conceived  a  notion,  which  I 
shall  submit  before  I  conclude,  concerning  the  excellence  of  some 
ancient  cements ;  but  lest  I  should  be  misled  by  it,  I  proceeded  in  all 
my  experiments  which  I  am  to  relate,  on  the  supposition  that  the  ex- 
cellence is  owing  to  some  matter  accidentally  introduced  in  the 
materials  which  the  ancients  found  in  the  districts  contiguous  to 
the  most  durable  cementitious  works,  or  designedly  blended  with  their 
mortar." 

Experiments  showing  the  integrant  parts  of  Gravel,  the 

CHOICE  AND  preparation  OF  IT,  AND  THE   EFFECTS   OF  ClAY, 

Fuller's  Earth,  and  Terras  in  Mortar. 

**0n  inspecting  different  kinds  of  gravel  used  in  London,  and  in 
divers  parts  of  England,  in  making  mortar,  I  observed  that  they 
all  contained  some  clay,  and  that  this  was  generally  colored  with 
martial  matter.  In  consideration  of  the  frequency  of  which  matter 
m  mortar  I  made  it  the  first  subject  of  my  present  inquiry. 

**By  theart  already  described,  I  sorted  three  bushels  of  screened 
gravel  dug  up  near  Portland  place,  in  Marylebone  parish,  into  five 
parcels ;  one  equivalent  to  our  rubble,  another  to  coarse  sand,  another 
to  our  Jine  Thames  sand,  another  to  our  finest  sand,  and  the  remain- 
der was  set  aside  as  clay  or  bolar  earth,  I  dried  all  these,  and  reduced 
the  lumps  of  clay  to  an  impalpable  powder. 

"Having  treated  divers  other  specimens  of  gravel  in  the  same 
manner,  I  found  that  gravel,  freed  from  the  larger  pebbles,  may 
generally  be  considered  as  a  native  mixture  of  rubble,  sand  and  clay ; 
and  that  when  the  clay  is  washed  out,  the  residuary  parts  of  different 
kinds  of  gravel  differ  in  size,  sharpness,  color,  and  hardness,  those 
being  the  hardest  which  consist  chiefly  of  quartoze  matter.  Judging 
of  gravel  according  to  the  precepts  derived  from  my  trials  of  sand,  I 


EXPERIIVIENTS  WITH  GRAVEL. 


71 


rank  that  dug  in  Marylebone  amongst  the  better  kinds  of  gravel, 
and  used  no  other  in  mortar. 

"After  a  great  number  of  trials  of  cements  made  with  my  best 
chalk-lime,  lime-water  and  the  gravel,  or  certain  parts  of  the  gravel, 
and  applied  on  tiles,  and  on  a  wall,  I  found  that  those  made  with  the 
coarse  and  fine  sand  of  the  gravel,  separated  from  the  rest  of  it,  and 
mixed  in  their  native  proportions,  were  the  best ;  that  those  made 
with  the  rubble,  coarse  sand,  and  fine  sand  mixed  in  their  original 
proportions,  but  containing  no  other  part  of  the  gravel,  were  the 
next  in  hardness,  and  the  other  desirable  qualities ;  that  those  con- 
taining all  the  parts  of  the  gravel,  except  the  clay,  in  their  native 
proportions,  differed  in  nothing  that  I  could  discover  from  these  last, 
for  the  finest  sand  of  this  gravel  was  not  a  fiftieth  part  of  the  mass  of 
it;  that  those  containing  the  rubble,  sands  and  clay,  in  the  same 
proportions,  and  those  made  with  the  unwashed  gravel,  appeared  on 
close  examination  to  be  the  worst  of  all  these,  and  those  containing 
the  native,  unwashed  gravel,  mixed  with  twice  its  proper  quantity  of 
the  clay  of  such  gravel,  showed  most  clearly  that  clay  is  highly  injuri- 
ous, by  disposing  the  mortar  to  crack  in  drying,  to  soften  in  wet 
weather,  and  to  moulder  when  the  quantity  of  clay  is  one-eighth  of 
that  of  the  sand,  but  in  much  smaller  quantities  it  only  prevents  the 
cement  from  acquiring  the  hardness  peculiar  to  good  mortar,  and 
consequently  disposes  it  to  perish  in  a  few  years. 

"With  my  best  mixtures  of  sands,  lime-water  and  lime,  I  blended 
fine  fat  tobacco-pipe  clay,  in  different  proportions,  and  exposing  these 
specimens,  I  perceived  that  the  efiect  of  the  clay  is  greater  as  it  is 
purer  and  fatter ;  the  specimens  in  which  the  quantity  of  fat  clay  was 
one-seventh,  or  one-eighth  of  that  of  the  sands,  mouldered  early  in  the 
winter  like  marl. 

"These  appearances  were  not  altogether  unexpected,  for  in  experi- 
ments formerly  made  with  a  view  to  the  improvement  of  fire- vessels, 
I  had  observed  that  clay  adheres  but  weakly  to  any  hard  bodies,  how- 
ever slowly  it  is  dried  on  them,  and  that  masses  composed  of  clay  and 


72 


VARIOUS  EXPERIMENTS. 


Band  in  divers  proportions,  never  acquired  any  considerable  hardness 
by  the  mere  drying  and  exposure  to  the  air.  It  was  not,  therefore, 
likely  that  clay  should  add  to  the  strength  of  mortar ;  but  as  dried 
clay  greedily  imbibes  water  and  swells  with  it,  and  in  drying,  con- 
tracts greatly  and  cracks,  if  anything  prevent  it  from  contracting 
equably;  and  as  marl-stones,  which  consist  of  clay  and  calcareous 
earth,  moulder  in  the  weather,  it  was  to  be  expected  that  clay  would 
be  hurtful. 

"  These  experiments  point  out  another  cause  of  the  defects  of  the 
common  mortar,  and  show  that  the  gravel  or  pit  sand  to  be  used  in 
any  valuable  building  ought  to  be  freed  from  the  clay  by  washing, 
which  will  be  found  a  very  cheap  operation,  >even  in  cities,  if  the  water 
which  carries  off  the  clay  be  directed  into  a  place  where  it  may  be 
depurated  by  subsidence,  for  repeated  use ;  they  likewise  direct  us  in 
the  examination  and  choice  of  these,  and  show  that  the  viler  kinds 
may  be  made  equivalent  to  our  best  mixtures  of  Thames  sand,  or 
nearly  so,  by  washing  or  sorting,  and  then  rejecting  the  excess  of 
rubble,  or  fine  sand. 

"I  must  observe,  however,  that  some  kinds  of  gravel  cannot  be 
made  fit  for  mortar  by  this  process,  for  the  grains  of  them,  which 
resemble  those  of  rubble  and  coarse  sand,  consist  of  smaller  grains  ce- 
mented by  clay,  which  is  so  far  indurated  that  it  cannot  difiiise  itself 
in,  the  water  speedily. 

Fuller'' s  earth  tried  in  the  same  manner  was  found  to  operate 
in  the  mortar  like  clay  in  every  respect,  as  I  might  have  presumed, 
except  that  the  former  was  less  injurious  than  the  clay,  when  the 
quantities  of  them  were  equal. 

«  Terras,  which  is  a  volcanic  production  consisting  chiefiy  of  clay 
and  calx  of  iron,  indurated  together,  when  it  was  ground  to  an  im- 
palpable powder,  produced  the  effects  of  Fuller's  earth,  in  mortar  the 
more  sensibly  as  it  approached  nearer  to  be  one-seventh  of  the  quan- 
tity of  sand.    The  coarser  powder  of  terras  has  the  same  effect. 

"A  mortar  made  of  terras  powder  and  lime,  was  used  in  wato. 


VARIOUS  EXPERIMENTS. 


73 


fences  by  the  Romans,  and  has  generally  been  employed  in  such  struc- 
tures ever  since  their  time.  It  is  preferred  before  any  other,  for  this 
use,  because  it  sets  quickly,  and  then  is  impervious  to  water,  whence 
some  people  hastily  conclude  that  it  is  the  best  kind  of  mortar  for  any 
purpose.  But  by  experience  I  know  that  mortar  made  of  lime  and 
terras  powder,  whether  course  or  fine,  will  not  grow  so  hard  as  mortar 
made  with  lime  and  sand,  but  on  the  contrary  is  apt  to  crack  and 
perish  quickly  in  the  open  air.  The  efficacy  of  it  in  water  fences  is 
only  experienced  where  it  is  kept  constantly  wet,  and  seems  to  de- 
pend upon  the  property  which  the  powder  of  terras  has,  in  common 
with  other  indurated  argillaceous  bodies,  and  especially  the  boles  (but 
in  a  higher  degree),  of  expediting  the  crystallization  of  the  calcareous 
matter,  by  imbibing  the  water  in  which  it  is  diffused  in  the  mortar, 
and  of  swelling  during  the  absorption,  so  much  as  to  render  the  ce- 
ment impenetrable  to  any  more  water;  it  seems  also,  that  an  acid 
of  the  vitriolic  kind,  which  is  contained  in  terras,  as  well  as  in  boles, 
contributes  to  the  speedy  setting  of  this  cement,  by  reducing  a  part 
of  the  lime  to  the  condition  of  gypsum." 

Experiments  showing  the  effects  op  Plaster-powder,  Alum, 
Vitriolic  Acid,  and  of  some  Metallic  and  Earthy  Salts 
AND  OF  Alkalies  in  Mortar.   Practical  Inferences. 

"In  my  best  mixtures  of  coarse  and  fine  Thames  sand,  with  one- 
seventh,  and  with  larger  quantities  of  lime,  I  tried  the  gypseous  pow- 
der of  which  plaster-of-paris  is  made,  and  found  it  to  be  injurious 
in  proportion  to  the  quantity  of  it.  The  particular  effects  of  gypsum 
in  mortar  were  such  as  might  be  expected  in  consequence  of  our 
knowledge  of  the  saline  nature  of  it,  gypsum  being  in  a  compound  of 
calcareous  earth  and  vitriolic  acid,  which  is  soluble  in  water,  not  so 
freely  as  neutral  salts,  but  rather  like  lime,  it  disposed  the  mortar  to 
set  faster  than  it  could  be  applied  in  stuccoing ;  it  contributed  very 
little  to  the  plasticity  of  it,  and  the  cement  was  the  more  apt  to  soften 
4 


74 


VARIOUS  EXPERIMENTS. 


in  wet  weather,  and  to  perish  in  time,  as  the  quantity  of  plaster-pow- 
der in  it  was  greater.  The  greater  quantity  tried  was  only  one-seventh 
of  that  of  the  sand. 

^'  Alum  was  found  very  injurious.  The  acid  of  alum  formed  silen- 
ite  or  gypsum  with  a  part  of  the  lime,  and  thus  operated  like  gypsum 
or  plaster-powder,  whilst  the  earth  of  the  alum  induced  the  imperfec- 
tions which  attend  the  use  of  clay.  The  greatest  quantity  of  alum 
used  was  one  part  in  ten  of  the  best  mixture  of  sand  and  lime,  and 
this  specimen  mouldered,  in  nine  or  ten  months,  like  marl. 

"  Vbtriolic  acid,  which  formed  silenite  or  gypsum  with  a  part 
of  the  lime,  produced  the  effect  of  a  quadruple  quantity  of  plastic  pow- 
der. 

Vitriols  of  lead  and  tin,  being  decomposed  by  the  lime,  operated 
like  smaller  quantities  of  vitriolic  acid.  Martial  vitriol  or  copperas  had 
the  same  effect,  and  induced  an  olive  color,  which  was  soon  turned  to 
that  of  rust. 

"  Vitriol  of  zinc,  or  white  vitriol,  and  Epsom  salt,  did  not  dispose 
the  mortar  to  set  hastily,  nor  injure  it  in  any  particular  discoverable 
during  the  application  and  drying  of  it,  for  these  vitriols  are  not  easily 
decomposed  by  lime ;  but  afterwards  I  perceived  that  they  impeded 
the  induration  of  the  stucco,  and  disposed  it  to  suffer  by  the  weather, 
the  more  as  the  quantity  of  either  came  near  to  be  one-tenth  of  the 
quantity  of  sand. 

Vitriolated  tartar,  Glauber's  salts,  and  the  salts  which  are  found 
in  most  of  our  waters,  such  as  sea-salt,  nitre,  marine  calcareous  salt, 
calcareous  nitre,  and  that  composed  of  magnesia,  and  marine  acid, 
were  found,  like  Epsom  salt,  to  injure  the  best  mortar ;  so  were  caustic 
mineral  alkali,  caustic  vegetable  alkali,  and  liquor  silicum.  Caustic 
volatile  alkali,  which  soon  exhales  by  reason  of  its  volatility,  had  no 
sensible  effect,  I  did  not  try  argol,  or  mild  alkalies,  because  they  re- 
duce the  lime  to  whiting,  neither  did  I  use  any  acid  which  forms  a 
very  soluble  salt  with  lime,  for  obvious  reasons. 

"Knowing  that  the  lime  which  has  been  employed  by  soap-boilers 


VARIOUS  EXPERIMENTS, 


75 


to  render  their  barilla  and  pot-ash,  caustic,  contains,  (even  after  the 
repeated  elixations,)  a  little  alkali  and  vitriolated  tartar,  blended 
with  the  calcareous  earth,  and  that  the  greater  part  of  this  last  is 
restored  to  the  condition  of  chalk,  by  the  acidulous  gas  imbibed  from 
the  alkaline  salts ;  I  had,  in  consequence  of  the  foregoing  experiments, 
sufficient  reason  to  presume  that  this  refuse  matter  of  soap-boilers 
cannot  answer  the  purposes  of  lime,  or  improve  our  mortar.  But  as 
a  pretence  to  the  contrary  is  made  by  some,  and  as  its  cheapness  is  a 
temptation  towards  the  use  of  it,  I  resolved  to  decide  this  question  by 
direct  experiment. 

'  *  After  trying  in  my  usual  manner,  specimens  of  mortar  made  with 
the  refuse  of  soap-lees,  and  my  best  sand,  in  different  proportions, 
and  others  made  with  this  sand,  lime,  and  the  refuse  matter,  in 
various  proportions,  I  found  the  first  destitute  of  the  most  useful 
properties  of  good  mortar;  and  the  others  were  defective  in  pro- 
portion to  the  quantity  of  the  refuse  matter  relatively  to  that  of  the 
lime.  Whether  this  matter  improves  mortar  made  with  gravel  and 
the  common  chalk  lime,  or  increases  the  defects  of  it,  is  a  question 
not  worth  our  notice. 

The  experiments  lately  related  show  that  lime  is  the  more  unfit 
for  building  and  external  incrustations  as  it  contains  more  gypsum, 
and  I  must  now  remark  that  most  kinds  of  limestone  used  in  England 
contain  considerable  quantities  of  this  matter,  which  is  not  much  cor- 
rected in  the  burning ;  but  as  I  have  in  the  second  section  enabled  my 
readers  to  discover  this  imperfection,  I  hope  I  shall  be  excused  from 
the  inviduous  office  of  deprecating  or  recommending  any  particular 
lime-stone,  or  manufactory  of  lime. 

"The  cautions  which  our  last-mentioned  experiments  suggest  in 
regard  to  the  use  of  water  are  especially  necessaiy  where  wells  and 
springs  abound  with  one  or  more  of  the  above-mentioned  salts,  and  it 
is  not  to  be  presumed  that  the  quantity  of  these  contained  in  water 
which  is  used  for  culinary  purposes  cannot  be  injurious  to  mortar,  for 
I  know  that  silenite,  Epsom  salt,  the  very  deliquescent  salts,  com- 


76 


VARIOUS  EXPERIMENTS. 


pound  of  magnesia,  and  marine  acid,  and  of  calcareous  earth  and  the 
same  acid,  may,  together  with  a  little  sea  salt,  be  natively  dissolved 
in  water,  to  the  quantity  of  half  an  ounce  in  a  gallon,  without  effect- 
ing the  taste  of  it  sensibly. 

When  we  consider  the  quantity  of  water  necessary  in  slaking  the 
lime,  making  the  mortar,  and  wetting  the  thirsty  bricks,  and  the 
smallness  of  those  portions  of  salts  whose  injurious  effects  were  dis- 
coverable in  the  course  of  one  year,  or  in  a  shorter  time,  we  find  suffi- 
cient grounds  for  concluding  that  such  saline  waters  will  be  found 
hurtful  in  mortar,  before  many  years  elapse,  particularly  where  it  is 
exposed  to  moisture.  Indeed  this  has  been  already  experienced  of  sea 
salt,  even  in  the  small  quantity  of  it  introduced  in  mortar,  when  the 
sand  is  taken  from  the  sea-shore. 

**The  easiest  method  of  discovering  the  quantity  of  saline  matter  in 
water,  consists  in  evaporating  it  slowly  to  dryness,  and  weighing  the 
residue.  Water  which  deposits  calcareous  earth  as  soon  as  it  is  heat- 
ed ought  to  be  cleared  by  subsidence  or  filtering,  before  the  evapora- 
tion is  completed. 

* '  When  a  choice  can  be  made,  rain  water  is  to  be  preferred,  river 
water  holds  the  next  place,  land  water  the  next,  spring  water  the  last, 
and  waters  noted  medicinally  or  otherwise  for  their  saline  con- 
tents ought  not  to  be  used  at  all  in  mortar,  for  the  salts  contain- 
ed in  them  are  those  which  were  tried,  the  vitriolated  tartar  ex- 
cepted." 

Experiments  showing  the  effects  of  Skimmed  Milk,  Serum 
OF  Ox-blood,  Decoction  of  Linseed,  Mucilage  of  Lin- 
seed, Olive  Oil,  Linseed  Oil,  and  Resin  in  Mortar,  and 
the  effect  of  painting  Calcareous  Incrustations. 

"  At  the  same  time  and  in  the  same  mixtures  of  the  best  sand 
and  lime,  I  tried  skimmed  milk,  serum  of  ox-blood,  decoction  of  lin- 
seed (strained),  and  thick  mucilage  of  linseed,  in  the  place  of  lime-' 
water. 


VARIOUS  EXPERIMENTS.  77 

"The  mortar  made  with  any  of  these  was  fatter  as  the  liquor  was 
more  glutinous,  but  was  as  liable  to  crack  as  mortar  made  with 
water.  In  the  course  of  a  year  it  appeared  that  each  of  these 
liquors  encourages  a  vegetation  to  take  place  on  the  surface,  which 
gives  it  an  ugly  appearance  and  tends  to  ruin  it,  and  that  they  all 
•  prevent  the  cement  from  acquiring  the  experienced  hardness  of  our 
best  compositions,  or  indeed  from  having  any  competition  with  them 
in  this  particular. 

The  notion,  therefore,  that  is  entertained  by  some  builders  con- 
cerning the  use  of  skimmed  milk  and  blood  is  erroneous,  unless  it 
be  confined  to  the  viler  kinds  of  mortar,  which  may  perhaps  be  im- 
proved by  them,  because  a  composition  of  sand,  whiting  and  mu- 
cilage grows  harder  than  that  of  whiting  and  sand  kneaded  with 
mortar. 

It  seems  that  glutinous  liquors  and  good  lime  act  reciprocally  on 
each  other,  in  the  time  of  mixing  them,  to  the  destruction  of  their 
respective  characters,  and  particularly  to  the  conversion  of  a  part 
of  the  quick  lime  into  whiting;  and  that  if  any  kind  of  mortar 
is  is  improved  by  them,  it  is  then  especially,  when  the  workmen 
takes  advantage  of  the  fatness  induced  by  them,  and  using  less 
than  his  customary  quantity  of  lime,  secures  his  work  from  crack- 
ing. 

Olive  oil,  mixed  with  good  mortar  or  substituted  in  the  place  of 
a  part  of  the  lime-water,  rendered  the  cement  defective,  as  the  quan- 
tity of  oil  was  greater.  The  greatest  quantity  used  was  half  that  of 
the  lime 

Linseed  oil,  used  in  the  same  manner,  makes  the  mortar  fatter, 
retards  the  drying  of  it,  and  prevents  it  from  acquiring  in  any  time, 
so  great  a  degree  of  hardness  as  it  otherwise  would  have.  It  was  the 
more  hurtful  as  the  quantity  of  it  was  nearer  to  that  of  half  the  lime, 
in  much  smaller  quantities  it  was  less  injurious  than  olive  oil.  From 
roy  observation  on  this  subject,  and  on  the  compositions  called  oil  ce- 
ments, I  have  reason  to  conclude  that  no  oil  ought  to  be  used  in  a 


78 


VARIOUS  EXPERIMENTS. 


cement  which  consists  chiefly  of  sand,  lime  and  water,  nor  any 
water,  or  watery  liquor,  in  a  cementitious  mixture,  which  is  moistened 
or  kneaded  with  oil  chiefly. 

As  linseed  oil,  whiting  and  sand,  make  a  cement  which  hardens 
to  a  great  degree  in  dry  situations,  and  abides  the  weather  a  long 
time  before  the  hardened  oil  relents,  it  is  not  improbable  that  linseed 
oil  may  meliorate  mortar  made  with  bad  lime.  But  good  lime  and 
linseed  oil  seem  to  injure  each  other,  in  forming  a  kind  of  saponaceous 
compound,  with  the  lime-water  of  the  mortar. 

From  the  experienced  effects  of  saline,  gelatinous  and  oleaginous 
matter,  I  infer  that  cow-dung,  which  I  have  not  tried,  would  impair 
good  mortar.  It  makes  the  common  mortar  fatter,  and  in  that  re- 
spect more  convenient  for  "  pargetting  "  the  interior  surface.of  chimney 
flues ;  it  seems  likewise  to  prevent  the  parget  made  with  bad  lime  from 
drying  so  quickly,  and  from  cracking  so  much,  as  it  otherwise  would 
do ;  the  fibrous  part  of  the  dung  contributing  largely  to  this  latter 
eflect.  On  these  grounds  it  may  be  useful  in  bad  mortar  thus  applied, 
whether  it  increases  the  hardness  of  it  or  not,  although  it  is  likely  to 
impair  good  mortar. 

^'•Powder  of  resin  intimately  blended  with  mortar  by  grinding  it 
with  a  part  of  the  lime,  and  lime-water,  was  hurtful  according  to 
the  quantity  of  it,  the  greatest  quantity  tried  being  one-fourth  of  that 
of  the  lime. 

Before  I  knew  the  event  of  these  experiments  I  made  an  incrusta* 
tion  on  a  wall  fronting  the  south,  but  shaded  from  the  sun  after  mid- 
day, with  a  cement  composed  of  seven  parts  of  my  mixed  sand,  one 
of  the  best  stone  lime,  and  the  necessary  quantity  of  lime-water.  As 
soon  as  the  incrustation  was  dry,  which  happened  in  four  days,  I 
painted  one-third  of  it  with  linseed  oil,  prepared  for  painter's  use,  an- 
other tl^ird  with  white  lead  paint,  and  the  remainder  was  separated 
from  these  by  a  channel  cut  between  them. 

"  After  fourteen  months,  the  last-mentioned  portion  was  very  hard 
near  the  surface,  and  the  induration  extended  very  deeply  into  the 


VARIOUS  EXPERIMENTS. 


79 


mass  of  it,  though  not  in  so  great  a  degree  of  perfection  as  that  of  the 
surface.  The  painted  portions  were  also  very  hard  at  the  surface,  but 
internally  much  weaker  than  the  other. 

*'From  my  observations  of  these  specimens,  and  of  divers  incrusta- 
tions in  this  city,  which,  being  made  of  bad  calcareous  cement,  have 
been  painted  and  sanded,  in  order  to  fill  the  cracks  and  fence  them 
from  the  weather,  I  have  had  sufficient  reason  to  conclude  that  an 
incrustation,  made  as  good  as  it  may  be  with  lime  and  sand,  and 
lime-water,  is  not  better  by  painting  it  as  soon  as  it  dries  ;  that  this 
covering  retards  the  induration  of  it,  by  cutting  off  its  communication 
with  the  air ;  that  it  therefore  renders  it  liable  to  be  irreparably  in- 
jured in  wet  weather  whenever  the  water  can  get  behind  the  paint ; 
and  that  if  paint  or  oil  ought  ever  to  be  applied  on  such  stucco,  it 
ought  not  to  be  used  in  less  than  a  year  after  the  incrustation  is  made. 
I  likewise  found  that  the  painting  and  sanding  of  the  common 
incrustations,  contributes  very  little  to  their  duration,  although  it 
hardens  them  at  the  surface,  for  it  does  not  effectually  prevent  them 
from  cracking,  and  it  avails  very  little  to  paint  the  cracked  stucco 
again,  because  cracked  stucco  is  always  *  hollow,'  as  the  workmen  term 
it,  that  is,  it  parts  from  the  wall  in  the  parts  contiguous  to  the  cracks, 
sounds  hollow  on  being  struck  with  the  knuckle,  and  falls  off  in  a  few 
years,  if  it  be  so  thick  and  large  in  extent  as  to  break  the  adhering 
portions  by  its  weight." 

Experiments  showing  the  effect  of  Sulphur  introduced 
INTO  Mortar  by  different  methods. 

"  In  my  first  trials  of  sulphur,  it  seemed  to  be  useful,  and  this  lea 
me  to  try  it  in  so  many  different  ways,  and  in  so  many  mixtures 
of  limes  and  sands,  and  of  these  with  flint-powder  and  divers  other 
substances,  as  would  render  the  recital  of  all  my  observations  on  the 
effects  of  it,  inconsistent  with  the  plan  of  this  essay ;  I  must,  there- 
fore, content  myself  with  communicating  those  which  I  think  most 


80 


VARIOUS  EXPERIMENTS. 


useful,  in  such  terms  as  may  give  some  intimation  of  the  manner  in 
which  the  experiments  were  made. 

**When  the  powder  of  sulphur  was  mixed  with  mortar  already 
made  of  good  materials,  and  did  not  exceed  one-thirty-second  part  of 
the  mass,  is  seemed  to  improve  it,  in  the  first  and  second  month,  and 
sometimes  during  a  longer  time  of  comparison  with  mortar  made  of 
all  the  same  materials  (except  sulphur)  in  the  same  proportions,  but 
in  ten  or  twelve  months  the  sulphur  was  found  to  be  injurious,  and 
the  more  so  as  it  exceeded  the  foregoing  proportion.  The  most 
hurtful  effect  of  it,  was,  its  disposing  the  mortar  to  relent  in  long  con- 
tinued rains,  and  become  quite  friable  after  a  few  alternatives  of  freez- 
ing and  thawing.  It  had  the  same  effect  in  mortar  containing  seve- 
ral of  the  ingredients  already  named,  and  of  those  hereafter  to  be 
mentioned. 

When  the  sulphur  was  mixed  with  fresh  powdered  lime,  and  these 
were  ground  briskly  with  lime-water,  a  calcareous  liver  of  sulphur 
was  formed,  proportionate  to  the  quantity  of  sulphur  used ;  and  the 
mortar  made  with  this  mixture  and  sand,  or  with  this  and 
sand  and  other  ingredients,  was  worse  than  mortar  contaning  an 
equal  quantity  of  the  sulphur  mixed  in  it  in  the  former  method. 

The  transparent  liquor  called  liquid  calcareous  liver  of  sulphur, 
which  consists  of  sulphur  dissolved  in  water  by  the  intervention  of 
lime,  being  used  instead  of  water  in  making  mortar  with  sand  and 
lime  in  any  proportions,  was  found  more  injurious  than  three  times 
the  quantity  of  undissolved  sulphur  was,  in  the  first-mentioned  method 
of  using  it,  and  this  liquor  had  the  like  efiect  in  mixtures  of  mortar 
with  divers  other  ingredients ;  whence  I  infer  that  sulphurous  miner- 
al waters  ought  not  to  be  used  in  mortar. 

"  If  the  plan  of  these  experiments  had  not  comprehended  the  noxi- 
ous as  well  as  the  useful  ingredients,  and  I  had  not  resolved  to  distrust 
every  theory,  I  might  have  foretold  the  event  of  these  mixtures,  in 
consequence  of  my  certain  knowledge  of  the  operation  of  sulphur, 
lime,  and  air  on  each  other. 


VARIOUS  EXPERIMENTS.  81 

"When  sulphur  and  lime  are  moistened  with  water,  and  exposed 
to  air,  the  acid  of  sulphur  being  attracted  by  the  lime,  whilst  the 
phlogiston  of  the  sulphur  is  attracted  by  the  air,  a  decomposition  of 
the  sulphur  takes  place,  and  new  compounds  are  formed.  The  acid 
and  lime  gradually  form  selinite,  or  gypsum,  whilst  the  air  combined 
with  the  phlogiston  is  wafted  away.  Therefore,  lime,  by  so  much  of 
it  as  is  thus  expended  in  forming  gypsum,  is  not  only  unable  to  act  as 
a  durable  cement  of  the  grains  of  sand,  but  is  capable,  according  to  the 
experiments  of  the  sixteenth  section,  of  counteracting  the  cementing 
power  of  the  residuary  part  of  it,  when  the  mass  of  sulphurated 
cement  is  exposed  to  the  weather. 

"The  pleasing  warm  color  which  sulphur  induces  in  calcareous 
stucco,  whilst  it  is  fresh,  and  the  promising  appearance  of  such  incrus- 
tations in  the  first  year,  have,  if  I  am  rightly  informed,  already  mis- 
led some  to  apply  it  freely  at  their  own  risk.  I  wish  these  observations 
may  serve  to  undeceive  them. 

"  About  this  time,  the  imitation  of  colored  stones,  by  incrustations, 
became  an  object  of  my  attention,  and  some  of  the  subsequent  experi- 
ments were  made  with  a  view  to  it,  as  well  as  to  the  purposes  already 
expressed." 

Experiments  showing  the  effects  op  Crude  Antimony,  Reg- 
uLus  OP  Antimony,  Lead  Matt,  Potter's  Ore,  White  Lead, 
Arsenic,  Orpiment,  Martial  Pyrites,  and  Slaked  Mundic, 
IN  Mortar. 

"  Crude  antimony  reduced  to  an  impalpable  powder,  and  then  ground 
with  the  lime,  and  lime-water,  operated  in  mortar  as  sulphur  does 
when  it  is  used  in  the  same  manner  and  in  the  quantity  which  the 
crude  antimony  contains. 

**The  antimonial  powder,  moreover,  induced  a  disagreeable  bluish 
color,  which  in  a  little  time  became  brown,  and  afterwards,  yellowish. 
When  the  powder  of  antimony  was  mixed  in  the  mortar  after  it  was 
made  it  was  less  injurious. 


82  VARIOUS  EXPERIMENTS. 

**  Regulus  of  antimony,  tried  in  the  same  way,  seemed  to  have  no 
other  effect  than  that  which  is  produced  by  the  admixture  of  flint 
powder,  or  other  fine  powders  of  hard  bodies. 

Powdered  lead  matt,  QXi(i  potter'' s  ore  of  lead  acted  like  crude  anti- 
mony but  more  slowly  and  weakly  in  equal  quantities  of  them. 

White  leadwsLS  found  exceedingly  injurious,  which  I  expected,  for 
I  had  long  before  discovered  and  shown  in  my  public  courses  on  chem- 
istry, that  a  great  part  of  white  lead  is  acidulous  gas,  into  which  vine- 
gar is  easily  convert  able  in  the  process  for  making  white  lead,  and  in 
many  others ;  and  I  foresaw  that  the  lime,  attracting  this  matter, 
would  be  reduced  to  the  condition  of  whiting  in  the  time  of  making 
the  mixture,  and  that  the  mortar  would  consequently  be  defective. 
The  white  lead,  as  fast  as  its  acidulous  gas  is  drawn  from  it  by  the 
lime,  becomes  yellow,  like  masticot.  As  white  lead  improves  the  oil 
cements,  these  experiments  show  that  there  is  no  true  analogy  be- 
tween the  calcareous  watyer  cements  and  those  which  are  called  oil 
cements. 

Arsenic  operated  in  mortar  like  the  neutral  salts,  and  orpiments 
produced  the  injurious  eflfects  experienced  of  sulphur  and  of  arsenic, 
which  effects  were  greatest  when  the  orpiment  was  ground  with  the 
unslaked  lime  and  lime-water.  Orpiment  imparted  a  dark  brown 
color  at  first,  which  soon  became  yellow  and  afterwards  disappeared. 

The  martial  pyrites,  called  mundic,  heated  to  redness,  and  then 
slaked  by  moistening  it  with  water  whilst  it  was  hot,  operated  like 
crude  antimony,  with  this  difference  only,  that  a  greater  quantity  of 
it  was  required  to  produce  the  same  effect ;  for  this  reason,  as  I  con- 
ceive it,  that  the  quantity  of  sulphur  in  martial  pyrites  is  less  than  in 
crude  antimony,  and  being  held  in  it  by  a  more  forcible  attraction,  is 
prevented  from  acting  as  freely  in  the  lime  of  the  mortar.  The  color 
induced  by  the  slaked  mundic  was  at  first  bluish,  and  afterwards 
turned  to  that  of  iron  rust. 

**  The  mundic  which  was  from  Cornwall,  used  in  its  native  state^  in 
mortar,  kept  me  in  suspense  upwards  of  twelve  months.  It  was  tried  not 


VARIOUS  EXPERIMENTS.  8? 

only  on  tiles  but  in  large  incrustations  on  walls,  because  it  promised 
great  advantages  at  first.  When  the  quantity  of  it  did  not  exceed 
one-twenty-fourth  of  that  of  the  mortar,  it  manifestly  increased  the 
induration  of  the  cement  during  the  first  nine  months,  but  after 
fourteen  or  fifteen  months  it  disposed  the  incrustation  to  relent,  the 
more  as  it  was  oftener  wetted,  or  as  the  place  was  damp,  and  from  be- 
ing exceedingly  hard,  to  become  penetrable  to  a  pointed  instrument, 
pushed  only  with  the  hand,  and  as  brittle  as  chalk-stone.  The  color 
and  changes  of  color  of  the  mortar  containing  native  mundic,  are 
similar  to  those  produced  by  the  slaked  mundic,  and  are  not  at  all 
pleasing  to  the  eye.  The  effects  of  much  smaller  quantities  of  this 
matter  in  mortar  do  not  yet  appear  so  clearly,  but  there  is  no  reason 
to  presume  that  they  will  not  be  of  the  same  kind,  though  in  a 
smaller  degree. 

"These  and  the  preceeding  experiments,  indicate  that  all  bodies 
soluble  in  water,  not  excepting  arsenic,  and  all  those  which  are  capa- 
ble of  efflorescing,  or  of  being  decomposed  by  air  and  moisture,  are 
hurtful  in  mortar ;  and  they  teach  us  to  avoid  those  kinds  of  gravel 
which  are  impregnated  with  pyritous  matter,  whether  it  be  arsenical, 
metalic,  aluminous,  or  calcareous. 

' '  The  effects  of  regulus  of  antimony,  and  the  speedy  decay  of  the 
cheaper  metals,  however  perfectly  they  are  de-sulphurated,  give  strong 
grounds  for  presuming  that  calcareous  cements,  which  are  to  be  ex- 
posed to  the  weather,  are  more  likely  to  be  injured  than  improved  by 
metallic  matter  introduced  in  any  form." 

Experiments  shovting  the  effects  of  Iron  Scales,  Washed 
CoLCOTHAR,  Native  Eed  Ochres,  Yellow  Ochres,  Umber, 
Powder  op  Colored  Fluor,  Colored  Mica,  Smalt  and 
other  colored  bodies,  in  Mortar.  Advice  concerning 
Colored  Incrustrations,  Inside  Stucco,  and  Damp  Walls. 

'■^  Iron  scales  from  a  smith's  forge,  which  consist  of  iron  semi-cal- 
cined, and  are  thought  by  many  to  improve  mortar,  were  tried 


84  COLOURED  MORTARS. 

eighteen  months  ago, (by  grinding  them  to  fine  powder,) and  mixing 
them  in  mortar,  to  half  the  quantity  of  lime,  and  in  smaller  proportions. 

**The  larger  quantities,  in  the  course  of  twelve  or  fourteen  months, 
appeared  to  be  hurtful ;  and  by  these  I  judge  of  the  smallest,  which  do 
not  yet  appear  to  produce  any  remarkable  effect  in  incrustations  made 
in  any  situations.  But  in  those  which  reached  near  the  ground,  and 
in  others  made  on  tiles  which  were  laid  flat  on  the  ground  in  a  shaded 
damp  corner,  in  both  of  which  instances  the  incrustations  were  always 
moist,  the  iron  powder  seemed  to  render  the  cement  a  little  harder 
than  it  would  otherwise  become  in  the  same  time  in  such  circum- 
stances, and  it  certainly  made  it  closer  in  the  grain. 

*'By  these  experiments,  I  am  inclined  to  think,  that  iron  powder, 
which,  during  its  conversion  to  rust,  imbibes  a  good  deal  of  acidulous 
gas  and  air,  and  swells  considerably,  may  be  used  with  success,  where 
the  proper  induration  of  good  mortar  is  prevented  by  continual  moisture, 
and  the  chief  purpose  of  the  cement  is  to  exclude  water  perfectly,  by  the 
closeness  of  its  texture,  to  which  the  swelling  of  the  iron  contributes 
not  a  little.  If  it  is  capable  of  producing  any  desirable  effects  in  ce- 
ments otherwise  circumstanced,  these  are  to  be  expected  only  when 
the  quantity  of  it  does  not  exceed  one-eighth  of  that  of  the  lime,  or 
one-fiftieth  of  that  of  the  mortar. 

' '  Washed  colcothar  of  iron,  native  red  ochres,  yellow  ochres,  and 
umber,  had  the  effects  of  smaller  quantities  of  terras,  or  of  equal 
quantities  of  flint  powder. 

"  Colored  fluor  and  micaceous  stones,  colored  marble,  smalt  and 
divers  other  colored  substances,  which  are  insoluble  in  water,  reduced 
to  fine  powder,  imparted  their  respective  tints  to  the  incrustations, 
but  acted  like  flint  powder. 

"From  the  experienced  effects  of  colored  calces  of  iron,  and  of 
divers  sulphurated  and  perishable  metallic  powders,  I  learned  that  these 
ought  not  to  be  used  in  external  incrustations,  since  they  render  them 
more  defective,  as  they  color  them  deeply ;  and  I  turned  my  thoughts 


COLOURED  MOKTARS. 


85 


to  the  discovery  of  some  other  expedient  for  inducing  permanent 
color,  without  injuring  the  cement. 

soon  found  that  this  may  be  done,  with  regard  to  the  lighter  and 
pleasanter  tints,  by  the  use  of  colored  sands,  or  the  coarse,  gritty  sorted 
powder  of  hard  and  durable  colored  bodies.  Lynn  sand  affords  a  white 
cement,  which  is  the  better  as  more  of  the  finest  part  of  the  sand  is 
sifted  out.  Thames  sand  makes  a  grey  cement,  not  unlike  Portland 
stone,  and  this  color  is  agreeably  varied  by  the  use  of  grey  bone-ash, 
of  which  we  shall  presently  treat. 

* '  A  rich  yellow  tint  is  obtained  by  using  the  golden  yellow  sand, 
of  which  kind  there  is  one  near  Croydon,  in  Surrey,  and  a  small 
quantity  of  which  mixed  with  Lynn  sand  gives  a  warm  white,  and 
with  Thames  sand,  an  exact  resemblance  of  Bath  stone.  These  are 
the  most  eligible  tints  for  the  fronts  of  houses. 

Until  I  had  tried  the  glistening  scaly  talcs,  I  imagined  that 
they  would  serve  to  impart  all  other  tints,  as  they  may  be  had  of  any 
color,  and  are  as  durable  as  they  are  pleasing  to  the  eye ;  but  they 
were  found  to  weaken  the  adhesion  of  the  cement  to  the  wall,  and  to 
make  it  so  rough  and  *  short '  that  it  was  almost  impossible  to  form  a 
smooth,  compact  incrustation  with  it,  unless  the  lime  was  used  in  an 
excessive  quantity,  and  in  the  course  of  eight  or  nine  months,  it  ap- 
peared that  the  cements  in  which  they  were  mixed  in  the  quantity 
necessary  to  produce  stone  tints,  were  rendered  spongy,  and  greatly 
weakened  by  them. 

"  Scaly  glistening  mica,  strewed  equally  on  an  incrustation,  pre- 
viously wetted  with  a  thin  mixture  of  lime-water  and  lime,  and  gently 
compressed,  to  lay  the  scales  flat,  imparts  the  color  with  the  fullest 
effects.  In  this  way,  colored  mica  may  be  used,  where  it  is  cheap,  on 
external  incrustations,  if  the  perspective  appearance  of  a  building  can 
be  improved  by  different  colors  of  any  members  of  it,  and  this 
kind  of  coloring  greatly  excels  painting,  in  the  fickle  weather  of 
our  climate,  because  it  lasts,  unfaded,  as  long  as  the  micaceous 
crust. 


86 


COLOURED  MORTARS. 


**To  tinge  a  cement  sufficiently  for  prospect  or  contrast,  of  any 
color  which  is  not  found  in  sand,  so  that  the  incrustation  shall  not  be 
impaired,  and  that  the  color  shall  be  as  durable  as  the  cement,  I 
found  nothing  more  advisable  than  to  use,  in  the  place  of  the  sand,  or 
of  a  part  of  it,  colored  glasses  or  colored  stones  of  the  hardest  kind, 
beaten  to  coarse  powder,  the  finer  parts  of  which  are  to  be  washed 
away,  not  merely  because  they  are  injurious  to  the  cement,  but  because 
I  observed  that  they  contribute  but  very  little  to  the  intended  color. 

*'The  drying,  induration  and  the  texture  of  incrustations  made  on 
brick  walls,  and  other  irregular  surfaces,  are  always  so  far  unequal  as 
to  exhibit  visible  traces,  which  deform  the  work,  and  cannot  be 
effectually  obliterated  by  any  known  method  so  convenient  as  that  of 
covering  the  first  coarse  incrustation,  after  it  has  dried,  with  another 
coat  which  may  be  finer  and  smoother.  Thus  the  expense  of  fine 
grained,  smooth  or  colored  stucco  is  rendered  moderate,  because  the 
finer,  or  the  coloring  materials  may  be  reserved  for  the  exterior  coat, 
which  will  last  for  ages  if  the  cement  be  good,  as  we  shall  show  when 
we  come  to  considerthe  experienced  duration  of  the  best  calcareous 
cements. 

•'As  the  mouldings  and  paintings  which  are  expended  on  the  soft 
stucco  now  used,  and  which  contribute  so  much  to  the  magnificence 
of  our  apartments,  can  be  equalled  in  their  ornamental  efiects  by  the 
double  incrustations  which  I  have  described,  and  greatly  exceeded  by 
these  last,  in  the  hardness  and  durability  of  them,  I  do  not  doubt 
that  plasterers  will  adopt  this  improved  method,  when  they  find  that 
it  is  consistent  with  their  own  interest,  as  well  as  that  of  their  em- 
ployers. I  am  not  sufficiently  acquainted  with  their  business  to  form 
a  just  estimate  of  this  subject,  but  I  will  submit  to  their  consideration 
a  few  observations  which  would  influence  me  very  much  in  the  choice 
of  stucco  for  a  house  of  mine. 

**The  compositions  heretofore  used  for  stuccoing  in-doors  are 
capable  of  hardening  considerably,  and  when  they  are  laid  on  the 
naked  walls,  soon  became  tarnished,  unsightly,  and  inconvenient,  by 


COLOURED  MORTARS. 


87 


the  damps  which  workmen  call  *  sweating, '  and  which  are  in  ray  opin- 
ion of  two  kinds,  one  I  will  call  damp  by  *  transpiration,'  and  the 
other  damp  by  'condensation.'  The  damp  by  transpiration  occurs 
when  the  principle  walls  are  stuccoed  before  they  have  dried,  or  when 
the  materials  of  them  are  so  spongy  as  to  imbibe  the  rain,  and  the 
circulation  of  the  air  within  the  house  is  not  sufficient  to  waft  away 
the  moisture  which  transudes  from  the  wet  wall  into  the  stucco,  and 
especially  when  the  exhalation  of  this  moisture  from  the  stucco  is  im- 
peded by  the  closeness  of  its  texture,  for  all  such  bodies  retain  moisture 
the  more  forcibly  as  their  pores  are  smaller  and  as  the  air  meets 
more  difficulty  in  pervading  them.  I  see  no  reason  to  doubt  that  this 
inconvenience  would  be  obviated  by  making  the  incrustation  of  a  tex- 
ture similar  to  that  of  the  materials  on  which  it  is  laid,  and  that  the 
cement  made  with  about  seven  parts  of  sand,  one  of  lime,  and  the 
lime-water,  and  improved  as  we  shall  teach  hereafter  by  the  admixture 
of  bone-ash,  would  continue  dry  in  such  circumstances,  because  mois- 
ture quickly  exhales  from  it,  by  reason  of  its  texture. 

''The  damp  which  seizes  incrustations  when  the  walls  are  badly 
constructed,  when  the  joints  of  the  facing  bricks  become  hollow  by  the 
decay  of  the  mortar,  or  when  the  copings  or  gutters  are  defective,  do 
not  fall  under  our  consideration. 

"The  damp  by  'condensation'  appears  most  in  the  finest  and 
closest  incrustations,  however  perfect  and  old  the  walls  may  be.  To 
find  the  proximate  cause  of  it,  we  need  only  to  advert  to  that  which 
gathers  on  glass  windows,  whilst  the  wainscot  and  other  spongy  bodies 
which  serve  to  enclose  the  same  rooms,  remain  dry,  or  to  the  moisture 
which  gathers  on  walls  faced  with  the  closer  kinds  of  ornamental 
marble,  in  sumptuous  buildings,  at  the  same  time  when  the  walls  and 
incrustations  contiguous  to  them,  and  are  of  a  coarse  texture,  are 
quite  dry.  In  these  and  other  instances  we  may  perceive  that  the 
damp  is  owing  to  the  closeness  of  these  bodies,  and  that  a  stucco  per- 
vious in  a  certain  degree  to  air  and  moisture,  will  be  free  from  it,  as 
well  as  from  the  other  lately  mentioned. 


88 


COLOURED  MORTARS. 


**  The  plasterers,  finding  their  stucco  which  is  as  fine  and  close  as 
they  can  make  it,  liable  to  contract  these  damps,  especially  on  the 
principal  walls  of  houses,  case  them  with  lath-work,  on  which  the  in- 
crustation is  laid,  distant  from  the  wall.  In  this  way  they  obviate  the 
appearance  of  damp,  but  they  at  the  same  time  contract  the  rooms, 
and  narrow  passages,  and  stair-cases  sensibly,  at  a  great  expense. 
This  is  enhanced  by  the  repeated  plastering  necessary  to  fill  the  slen- 
der cracks  which  disfigure  their  incrustation  during  the  drying,  and 
Dy  the  oiling  or  painting  which  is  finally  required  to  hide  this  defect 
completely,  if  not  to  give  color.  Thus  the  work  becomes  costly,  al- 
though the  plasterer's  profit  is  moderate. 

*^0n  these  considerations  I  am  inclined  to  the  opinion  that  it  will 
be  found  as  advantageous  to  the  plasterer  as  to  his  employer,  to  prefer 
our  cement  before  any  other,  for  internal  incrustations,  especially 
when  no  other  color  is  required,  besides  those  which  may  be  imparted 
by  colored  sand,  or  materials  which  do  not  greatly  exceed  it  in  price. 
I  would  not  interfere  with  the  workman  in  forming  an  exact  com- 
parative estimate  of  the  expenses,  if  I  could  do  it,  but  I  will  venture 
to  affirm  that  an  incrustation  made  as  I  have  described,  or  in  the  im- 
proved method  hereafter  to  be  shown,  will  be  found  ultimately  cheaper 
than  any  other  yet  discovered,  for  the  following  reasons,  viz. :  It  will 
be  more  durable  by  reason  of  its  greater  hardness ;  it  will  retain  its 
color  longer  unfaded,  because  the  coloring  materials  do  not  tarnish, 
or  perish  the  paint ;  it  will  preserve  the  sharpness  of  the  moldings, 
and  the  elegance  of  its  appearance  longer,  because  it  will  not  require 
the  frequent  painting,  which  soon  blunts  the  figures  and  moldings  of 
ordinary  stuccoes ;  it  may  be  finished  with  less  labor,  because  it  is 
not  apt  to  crack  in  these  circumstances,  and  does  not  need  many 
coats  and  repeated  plastering ;  and,  as  it  is  not  likely  to  contract 
damp,  it  will  save  all  the  expenses  and  inconveniences  of  lath-work, 
whether  it  be  laid  on  partitions  or  on  principal  walls,  provided  the 
cement  applied  on  the  former  be  made  of  the  finest  materials. 

If  a  polished  and  white  surface  of  our  stucco  should  be  required, 


WOOD  ASHES,  ETC.,  IN  MORTAR. 


89 


it  ought  to  consist  of  two  layers ;  the  first  of  which  is  to  be  coarse, 
and  capable  of  hardening  to  the  highest  degree,  the  second  is  to  con- 
sist of  flint  powder,  lime,  and  lime-water,  and  is  to  be  laid  on  very- 
thin,  and  finely  smoothed.  To  give  a  rich  color  together  with  a 
smooth  surface  to  our  best  incrustations,  we  must  use  tin  the  place  of 
flint  powder  for  the  finishing  coat,  the  colored  powder  of  sands,  or 
stones,  or  glasses,  and  introduce  as  much  of  the  coloring  ingredients 
used  in  painting  as  will  be  sufiicient  to  givQ  the  required  appearance, 
avoiding  those  which  are  spoiled  by  lime, 

"To  my  eye,  the  warm  white,  or  colored  stucco,  which  is  not  quite 
smooth,  is  the  pleasantest,  but  those  who  prefer  the  smoothest,  may 
have  it  made  at  a  moderate  expense,  in  this  last-mentioned  method, 
in  which  the  useful  and  solid  part  of  it,  contributes  to  the  support  and 
duration  of  the  weaker  ornamental  coat,  which  thus  circumstanced  is 
likely  to  preserve  its  beauty  for  a  very  long  time,  although  it  might  in 
the  weather  be  impaired  in  three  or  four  years." 

Experiments  showing  the  effects  of  common  Wood  Ashes, 

CALCINED  OR    PURER  WoOD  ASHES,   ElIXATED  AsHES,  CHAR- 
COAL Powder,  Sea-coal  Ashes,  and  Powdered  Coke,  in 
.   Mortar;  and  Observations  on  their  integrant  parts,  and 
the  differences  between  them  and  the  powders  of  other 

BODIES. 

"  The  ashes  of  wood  and  sea-coal,  are  frequently  mixed  with  mor- 
tar, or  used  in  the  place  of  sand,  in  laying  tiled  floors,  and  even  in 
external  incrustations.  Some  workmen  say  they  are  used  in  the  for- 
mer case  to  save  sand,  others  that  they  serve  to  resist  moisture,  and 
those  who  seem  to  be  the  best  informed  afiirm  that  they  hasten  the 
drying  and  induration,  and  prevent  the  cracking  of  mortar  which  is 
laid  very  thick  in  order  to  fill  the  depressions  of  walls  which  are  to  be 
stuccoed ;  and  that  they  are  used  in  finer  incrustations  with  the  sole 
riew  of  preventing  cracks. 


90  WOOD  ASHES,  ETC.,  IN  MORTAR. 


"  The  ashes  of  the  same  kind  of  wood,  differ,  according  to  the  cir- 
cumstances in  which  they  are  formed,  even  upon  the  same  hearth,  not 
only  in  color,  but  in  other  particulars  known  to  chemists,  which  I  shall 
attend  to  presently.  As  the  separation  of  these  different  sorts  of  ashes 
is  not  practicable  at  a  moderate  expense,  and  is  never  attempted  by 
the  workmen,  I  contented  myself,  at  first,  with  procuring  the  ashes 
of  cleft  pollards,  burned  on  the  hearth,  and  with  sifting  the  whole 
quantity  of  them,  to  free  the  finer  parts  from  the  fragments,  and 
coarse  powder  of  charred  wood,  which  formed  a  great  part  of  the 
bulk  of  them.  The  sifted  ashes  were  gray,  inclining  to  brown, 
strongly  alkaline  to  the  taste,  and  viewed  through  a  convex  lens, 
were  found  to  contain  a  considerable  quantity  of  fine  charcoal  powder, 
which  I  estimated  at  one-sixth  or  more  of  the  bulk. 

"To  learn  the  effect  of  the  purer  ashes,  or  of  the  more  dephlogis- 
ticated  earthy  and  saline  parts,  separated  from  the  charcoal,  I  took 
about  a  gallon  of  the  sifted  ashes,  and  burned  them  on  a  test  in  a  re- 
verberatory  furnace,  with  a  heat  not  exceeding  that  of  a  culinary  fire, 
taking  care  to  accelerate  the  combustion  of  the  charcoal  powder  con- 
tained in  them,  and  render  it  equable  through  the  whole  heap  by 
stirring  it,  and  presenting  fresh  surfaces  to  the  air,  until  the  whole 
was  rendered  incombustible.  After  this  process,  the  powder  which  I 
shall  call  calcined  wood  ashes,  was  rather  brown  than  gray,  and  re- 
tained its  saline  taste. 

''On  trying  the  sifted  wood-ashes  in  my  best  mortar,  and  in  other 
mixtures  of  sand  and  lime,  I  found  that  they  gave  the  cement  a 
spongy  texture,  and  enabled  it  to  dry  without  cracldng,  when  the 
lime  was  not  used  in  excessive  quantity,  but  that  they  prevented  it 
from  acquiring  the  hardness  of  mortar  made  of  lime  and  sand  only ; 
so  that  the  advantages  they  promised  to  afford  in  certain  circum- 
stances appeared  to  be  counterbalanced  by  the  permanent  weakness  in- 
duced by  them ;  which  latter  effect  was  the  greater,  as  the  quantity 
of  the  ashes,  came  nearer  to  equal  that  of  the  lime. 

"The  calcined  wood-ashes  likewise  prevented  the  mortar  fi'ora 


WOOD  ASHES,  ETC.,  IN  MORTAR.  91 

2racking,  without  making  it  so  spongy,  but  they  materially  impeded 
the  induration  of  it,  and  disposed  it  to  be  injured  by  rain,  in 
the  same  manner  as  small  quantities  of  alkali  were  found  to  do. 

*'0n  a  strict  comparison,  the  calcined  wood-ashes,  which  wc  may 
consider  as  ashes  freed  from  the  charcoal  powder,  appeared  to  be 
much  more  injurious  than  the  uncalcined.  This  I  imputed  to  the 
greater  quantity  of  alkali  in  the  former,  which  is  hurtful  in  a  double 
capacity,  first,  as  a  saline  body,  and  secondly,  as  a  compound  which 
yields  its  acidulous  gas  to  lime,  in  the  instant  of  mixture,  and  con- 
sequently impairs  the  cement. 

Mortar  made  with  bad  lime  in  the  usual  proportions  may  never- 
theless be  improved  by  sifted  wood-ashes ;  for  the  coal  and  earthy 
parts  of  these,  if  they  were  only  equivalent  to  so  much  sand,  render  it 
less  liable  to  crack  ;  and  the  bad  effect  of  the  alkali,  may  be  greatly 
overbalanced  by  this  advantage,  in  an  incrustation  which  is  required 
to  be  rather  uniform  and  secure  from  clacking,  than  hard  and  durable 
in  the  highest  degree. 

must  not  omit  this  opportunity  of  observing  that  calcined  wood- 
ashes,  and  even  the  sifted  fresh  wood-ashes,  improve  p(aster-of-paris, 
in  hardness,  to  a  very  great  degree,  if  it  be  kept  in  a  dry  place.  The 
solution  of  this  phenomenon  is  not  difiicult. 

"Any  person  who  intends  to  repeat  my  experiments  on  calcined 
wood-ashes  ought  so  take  care  that  they  be  not  calcined  with  a 
stronger  heat  than  I  described,  for  if  he  exceeds  this,  the  ashes,  after 
the  signs  of  their  combustion  have  ceased,  will  smoke  strongly,  a  part 
of  the  saline  matter  being  sublimed  in  the  meantime,  and  the  remain- 
ing earthy  and  saline  portion  will  form  a  light  gray  or  brown,  semi- 
vitrified,  gritty  powder,  or  will  concrete  in  lumps.  This  matter  will 
then  be  found  insipid,  and  equivalent  to  sand,  in  mortar,  as  I  have 
experienced,  for  it  differs  as  much  from  wood-ashes,  as  the*  powder  of 
potter's  stoneware  differs  from  the  raw  clay. 

'•Whilst  I  was  employed  in  these  experiments  the  following 
thoughts  occurred  to  me.    The  ashes  used  by  workmen  being  passed 


92  WOOD  ASHES,  ETC.,  IN  MORTAR. 


througli  a  coarse  sieve  may  consist  for  the  greater  part  of  charcoal 
which  afterwards  is  beaten  finer  in  making  the  mortar. 

**The  ashes  used  by  builders,  whose  durable  works  authorized  this 
practice,  might  have  been  the  refuse  of  manufactories  of  potash,  into 
which  the  saline  matter  is  always  carefully  extracted  from  them ;  and 
charcoal  powder,  or  elixated  ashes  may  greatly  improve  mortar,  al- 
though ashes  finely  sifted  and  replete  with  salts  would  impare  it.  I 
therefore  boiled  my  calcined  wood-ashes  in  water,  and  repeated  this 
operation  twice  in  fresh  water,  knowing  that  one  elixation  does  not 
free  the  ashes  perfectly  from  the  saline  matter.  I  then  dried  the  in- 
sipid ashes  thoroughly  and  used  them  in  this  state,  under  the  name  oi 
elixated  wood-ashes.  At  the  same  time  I  pro\ided  charcoal  powder 
sifted  through  the  same  sieve  which  I  used  for  the  wood-ashes. 

"After  a  great  many  experiments  made  in  the  usual  manner  with 
the  elixated  ashes,  I  found  that  they  rendered  the  mortar  spongy,  dis- 
posed it  to  dry  and  harden  quickly,  and  prevented  it  from  cracking, 
more  eifectually  than  the  like  additional  quantity  of  sand  would  do  it. 
They  did  not  appear  to  induce  the  defects  attending  saline  bodies  in 
mortar,  they  only  made  it  weaker,  as  the  quantity  of  the  elixated 
ashes  was  greater  relatively  to  that  of  the  sand  and  lime. 

"  This  weakness,  however,  was  not  such  as  the  unwashed  ashes  or 
saline  bodies  produce,  but  rather  of  the  kind  which  I  pointed  out  in 
those  parts  of  the  foregoing  sections,  wherein  I  endeavored  to  show 
that  cementitious  masses  resist  edged  instruments,  or  any  force  tend- 
ing to  break  them,  the  more  weakly  as  they  contain  more  of  the 
softer  and  brittle  calcareous  matter,  or  as  softer  grains  are  substituted 
for  a  part  of  the  sand. 

*^In  every  comparison  of  the  specimens  containing  unwashed  wood- 
ashes,  with  those  in  which  the  elixated  ashes  were  mixed  in  the  same 
proportions,  it  clearly  appeared  that  the  latter  are  to  be  preferred,  and 
that  neither  of  them  ought  ever  to  exceed  half  the  quantity  of  lime, 
in  good  mortar. 

As  flint  powder  and  other  earthy  powders  were  found  to  dispose 


WOOD  ASHES,  ETC.,  IN  MORTAR. 


93 


mortar  to  crack,  I  could  not  conceive  how  the  elixated  wood-n  lies 
operated  so  elFectually  in  preventing  this  defect,  until  I  examined  them 
attentively,  and  found  them  to  differ  from  the  other  powders  in  two 
particulars.  Elixated  wood-ashes  contain  very  little  powder  of  the 
finer  kind,  they  feel  gritty  between  the  fingers,  and  appear  to  consist 
of  ragged,  spongy,  small  grains,  compressible  to  a  considerable  degree 
in  the  heap.  How  a  powder  thus  conditioned  prevents  the  crack- 
ing of  mortar  or  otherwise  improves  it,  I  shall  attempt  to  explain 
after  stating  other  facts  upon  which  my  notions  of  this  subject  are 
founded. 

"  Charcoal  powder  had  the  same  effects  as  elixated  wood-ashes, 
with  these  differences  only,  that  the  cements  containing  the  larger 
quantities  of  charcoal  powder  could  be  more  easily  cut,  and  were  of  a 
bluer  color,  than  those  containing  the  like  quantities  of  elixated  wood- 
ashes.  The  powder  which  I  used  when  sifted  like  the  ashes,  and  viewed . 
through  a  microscope,  answered  to  the  description  lately  given  of  elix- 
ated ashes. 

The  screened  ashes  of  Newcastle  coal  consist  chiefly  of  charred 
coal  or  coke,  and  as  they  contain  very  little  saline  matter,  are  insipid. 
When  I  reduced  them  to  powder,  and  passed  them  through  the  sieve, 
they  answered  to  the  description  given  of  elixated  wood-ashes  and 
produced  nearly  the  same  effects  in  mortar.  They  did  not  weaken  it 
BO  much  as  charcoal  powder  had  done,  which  I  impute  to  the  greater 
hardness  of  the  small  grains  of  coke. 

*'In  all  these  comparisons,  it  is  to  be  understood  that  I  made 
them  at  the  same  periods  of  the  induration  of  the  several  specimens. 

**From  these  experiments,  I  conclude  that,  where  a  choice  can  be 
made,  these  powders  are  eligible  in  this  order :  1.  Elixated  wood-ashes 
freed  from  the  finest  powder  in  washing ;  2.  Powdered  coke  or  sea- 
coal  cinders ;  3.  Charcoal  powder ;  4.  Rough  wood-ashes,  powdered. 
But  well-burned  fine  unwashed  wood-ashes,  ought  not  to  be  used  at  all 
in  external  cementitious  work,  or  incrustation. 

**The  last  of  these  gives  a  disagreeable  gray  or  dusky  color  to  the 


94 


WOOD  ASHES,  ETC.,  IN  MORTAR. 


cement ;  and  the  others  a  bluish  or  slate  color,  still  more  offensive  to 
the  eye,  for  which  reason  they  are  unfit  for  any  work  that  is  not  hid 
iTom  the  view. 

As  my  reader  may  not  fully  understand  what  I  briefly  mentioned 
concerning  the  sensible  difference  between  these  last  examined  pow- 
ders and  others  noticed  in  the  preceding  sections,  I  will  thus  exem- 
plify my  notions. 

Wood  consists  of  watery  and  volatile  parts  which  are  expelled  by 
heat,  and  of  fixed  parts  which  constitute  the  charcoal ;  and  charred 
wood,  which  greedily  imbibes  air  or  water  in  great  quantity,  may 
be  considered  as  an  assemblage  of  capillary  tubes  of  divers  figures 
and  sizes.  So  we  may  likewise  consider  the  fragments  of  charcoal, 
each  a  visible  grain  of  its  powder.  But  as  the  most  brittle  bodies 
are  flexible  when  they  are  made  sufficiently  thin,  the  charcoal  pow- 
der is  an  assemblage  of  small  flexible  or  compressible  tubulated 
bodies. 

"  As  the  charcoal  which  is  the  fixed  and  more  solid  basis  of  wood, 
is  spongy  after  the  juices  are  expelled  in  charring ;  so  the  ashes  of 
charred  wood  are,  after  the  elixation,  an  assemblage  of  spongy  or 
tubulated  grains  out  of  which  the  phlogistic  matter  has  escaped  during 
the  combustion,  and  the  texture  of  these  grains  differs  from  that  of 
the  grains  of  fine  sand,  or  of  flint  powder,  in  the  same  manner,  if  not 
in  the  same  degree,  as  the  texture  of  sponge  differs  from  that  of  flint, 
And  we  may  conceive  the  unwashed  wood-ashes  as  a  heap  of  small 
spongy  bodies  clogged  with  alkaline  salt. 

"Upon  the  same  grounds,  the  relation  of  coke  or  sea-coal  cinders 
to  the  raw  coal  is  analagous  to  that  which  charcoal  bears  to  wood,  or 
spongy  pumice  stone  to  porphyry ;  and  transferring  these  observations 
to  bones,  and  considering  the  smaller  vessels  and  finer  texture  of 
them,  than  of  wood,  we  shall  find  the  powder  of  charred  bones 
to  consist  of  tubulated  or  spongy  bodies  like  those  of  charcoal 
powder,  but  pervious  by  slenderer  and  harder  tubes,  and  bone- 
ash,  which  is  the  gritty  powder  of  well-burnt  bones,  to  have  the  same 


/  BONE  ASHES  IN  MORTAR.  95 

relation  to  the  charred  bones  as  eJixated  wood-ashes  have  to  cliarcoal 
powder. 

^'Thuslhave  thought  of  these  substances  after  having  observed 
what  happens  to  them  in  the  preparation ;  examined  them  hy  sl  mi- 
croscope, experienced  their  effect  to  be  so  different  from  those  of  iinest 
sand,  or  pov^dered  stones  in  mortar,  and  finally  discovered  by  repeated 
experiments,  the  detail  of  which  is  not  now  necessary,  that  semi- vitri- 
fication, which  destroys  the  spongy  texture,  and  levigation  which 
breaks  these  spongy  grains  down  to  the  particles  of  which  they  are 
constructed,  render  charcoal  powder,  wood -ashes,  powdered  sea-coal 
cinders  and  others  of  the  like  kind,  incapable  of  acting  in  the  man- 
ner described  in  calcareous  cements. 

**A11  these  things  being  considered,  I  impute  the  effects  of  these 
ashes,  or  powders,  to  the  tubulated  structure  and  compressibility  of 
the  integrant  parts  of  them,  and  in  the  next  section  I  shall  offer  all 
that  I  have  attempted  further,  theoretically  or  practically,  relative  to 
this  subject." 

Experiments  showing  the  effects  of  White  and  Gray  Bone- 
Ashes,  AND  the  Powder  of  Charred  Bones,  and  Theory 
OF  the  Agency  of  these  in  the  best  Calcareous  CEMENXii. 

"Long  before  I  had  tried  all  the  powders  heretobefore mentioned, 
I  used  bone-ashes  in  many  experiments,  and  saw  the  effects  in 
mortar.  For  the  sake  of  brevity  and  perspicuity,  I  reserved  the  rela- 
tion of  them  for  this  section :  and  in  order  to  show  more  clearly  the 
analogy  in  texture  between  bone-ashes  and  the  powders  lately  men 
tioned,  and  to  suggest  the  means  of  procuring  them  in  any  part  of 
this  country,  I  will  premise  a  sketch  of  the  most  profitable  processes 
by  which  they  are  prepared,  at  a  moderate  price  not  exceeding  that  of 
good  lime. 

"The  bones  collected  in  great  cities  are  broken  to  small  fragments 
in  a  mill,  and  boiled  in  water,  in  order  to  extract  and  save  the  oil  of 


96 


BONE  ASHES  IN  MORTAR. 


them.  They  are  tlien  put  into  a  large  iron  *  still,*  through  an  aper- 
tiire  which  is  stopped  up  closely  after  the  charge  is  made,  The  still, 
which  opens  into  an  apparatus  of  refrigeratory  vessels,  is  h(jated  grad- 
ually to  redness,  until  all  the  volatile  alkali,  commonly  called  spirit, 
find  salt  of  hartshorn,  is  expelled  from  them,  together  with  the  empy- 
reumatic  oil,  water,  and  certain  elastic  invisible  fluids.  The  alkali 
being  the  only  valuable  article  amongst  these,  is  retained  and  con- 
densed in  the  refrigeratory  tubes  and  vessels,  with  all  possible  care, 
whilst  the  lactic  fluids,  lest  they  should  burst  the  vessels,  are  sufFerea 
to  escape  in  places  distant  from  the  fire,  or  the  flame  of  candles,  be- 
cause they  are  combustible,  and  if  they  catch  fire  whilst  air  remains 
in  the  condensing  vessels,  explode  like  gunpowder. 

*'The  bones  thus  heated,  without  being  exposed  to  the  air,  are 
charred  to  blackness,  but  still  remain  combustible.  When  they  are 
required  in  this  state,  the  iron  still  is  kept  closed  until  they  are 
cool,  and  then  the  blackest  of  them  are  ground  to  fine  powder,  which 
is  used  as  a  substitute  for  ivory  black,  which  is  prepared  in  the  same 
way  from  ivory.  The  coarser  powder  of  these  is  what  I  understand  by 
powder  of  charred  bones.  But  when  this  is  not  the  manufacturer's 
design,  the  door  of  the  iron  still  is  left  open  whilst  it  is  hot,  and  the 
charred  bones  which  flame  and  burn  when  they  meet  the  air  are 
thrown  into  a  kind  of  kiln,  at  the  bottom  of  which  the  air  can  freely  en- 
ter, and  maintain  the  combustion  until  the  bones  are  burned  to 
whiteness  for  the  greater  part.  The  white  fragments  are  picked,  and 
rather  bruised  than  ground  to  a  gritty  powder  by  a  millstone,  which 
rolls  over  them  vertically  on  an  inclined  circular  plane.  This  powder, 
passed  through  a  sieve,  is  called  bone-ashes^  which  are  much  used  in 
metallurgy,  and  fitter  for  our  purposes  in  incrustations  than  the  pow- 
der of  burned  bones,  ground  as  pigments  are.  The  fragments  which 
have  not  been  thoroughly  burned  in  the  kiln  form  a  dark  grey  powder, 
and  the  mixtures  of  white  and  grey  burned  bones  afford  bone  ashes  of 
the  lighter  grey  colors. 

"  The  whole  quantity  of  bone  -ashes,  which  is  to  be  used  in  the  same 


BONE  ASHES  IN  MORTAR. 


97 


incrustation,  ought  to  be  well-mixed,  for  it  is  impossible  to  sort  the 
well  burnt  or  the  gray  bones  so  accurately  as  to  secure  an  unity  of 
color  in  the  parcels  of  powder  which  are  successively  prepared,  and  a 
very  small  variation  in  the  color  will  be  apparent  in  the  incrustation. 

Knowing  that  bone-ashes  consist  chiefly  of  calcareous  earth,  and 
may  be  reduced  to  lime  by  dissolving  them  in  acids,  precipitating  the 
solution  by  alkalies,  washing  the  precipitate  perfectly,  and  then  burn- 
ing it.  I  tried  them  with  sand  in  different  ways,  in  order  to  learn 
how  far  they  resemble  lime  in  their  cementing  properties,  and  found 
that  the  sorted  bone-ashes  had  very  little  effect,  but  that  the  composi- 
tions made  with  the  levigated  powder  of  these,  and  sand  and  water, 
were  nearly  equal  in  hardness  to  those  made  with  whiting  and 
sand,  kneaded  with  water,  in  the  same  proportion,  and  were  not  so 
liable  to  crack.  Hence  I  inferred  that  bone-ashes,  of  which  five-sixths 
are  calcareous  earth,  could  not  improve  mortar  by  any  augmentation 
of  the  cementing  powers  of  the  lime,  although  they  might  be  useful  in 
other  respects,  and  that  they  could  not  supply  the  defect  of  lime,  in 
quantity  or  quality. 

*'In  the  course  of  two  years  I  made  so  many  experiments  with 
bone-ashes,  mixed  in  mortar  composed  of  lime,  sand  and  lime-water, 
in  different  proportions,  and  of  these  with  divers  other  ingredients, 
that  I  may  venture  to  say,  I  attained  a  thorough  knowledge  of  their 
effects,  and  need  not  hesitate  to  relate  them  in  the  style  of  precept. 

"The  sorted  bone-ashes,  mixed  with  mortar,  in  any  quantity  not 
exceeding  that  of  the  lime,  dispose  the  cement  to  set  speedily,  without 
cracking,  and  effectually  secure  it  from  cracking,  if  it  does  not  con- 
tain lime  in  superfluous  quantity.  They  likewise  give  a  texture 
which  is  the  more  spongy  as  the  quantity  of  bone-ashes  is  greater,  and 
they  accelerate  the  induration  of  it,  through  the  whole  mass. 

*'The  sorted  bone-ashes  increase  the  plasticity  of  fresh  mortar 
which  is  made  with  the  smaller  quantities  of  lime,  in  order  to  secure 
the  woi-k  from  fissures,  and  thus  they  are  useful  in  a  triple  view,  in 
external  incrustations,  by  facilitating  the  operation  of  plastering,  b^ 


98 


BONE  ASHES  IN  MORTAR. 


preventing  cracks,  and  by  bringing  the  incrustations  quickly  to  a  state 
in  which  it  is  not  easily  injured  by  rain. 

"When  the  sorted  bone-ashes  exceed  the  lime  in  quantity,  they  sen- 
sibly injure  the  cement  by  rendering  it  weaker.  How  these  ashes, 
which  are  not  equivalent  to  sand  in  the  hardness  of  their  grains,  nor 
to  lime  in  their  cementing  powers,  operate  to  weaken  the  cement  may 
be  easily  conceived,  in  consequence  of  the  observations  made  in  the 
ninth,  twelfth,  and  thirteenth  sections.  And  when  they  are  mixed  in 
mortar,  in  the  quantity  of  one-fourth  of  the  lime,  they  improve  the 
plasticity,  if  the  mortar  be  *  short,'  and  they  produce  the  desirable  elfects 
above-mentioned  in  a  sensible  degree,  without  weakening  the  cement 
in  the  same  proportion.  As  a  smaller  quantity  of  them  seem  to  be 
useless,  and  a  greater  quantity  than  that  of  the  limes,  injurious,  the 
following  rules  are  to  be  observed : — 

*'When  it  is  required  more  to  secure  an  incrustation  from  the 
effects  of  hot  weather,  to  finish  it  quickly,  to  hide  the  traces  of  brick- 
work, which  are  apt  to  appear  through  it,  and  to  guard  it  against 
rain,  than  to  make  it  hard  and  durable  in  the  highest  degree,  as  much 
sorted  bone-ashes  must  be  used  as  lime.  When  the  season,  exposure, 
and  other  circumstances  permit  to  attend  solely  to  the  true  excellence 
and  duration  of  the  work,  there  must  be  used  in  our  best  calcareous 
cement  only  one  part  of  the  sorted  bone-ashes  for  every  four  parts  of 
lime.  By  these  rules  the  operator  may  choose  intermediate  quantities 
adapted  to  his  purposes. 

*'The  coarser  bone-ashes  used  in  making  cupels,  and  tests,  do  not 
go  so  far  (so  the  workmen  express  themselves)  or  do  not  operate  so 
effectually  as  the  sorted  ashes  in  equal  quantities  of  them,  by  weight ; 
and  finer  or  levigated  bone-ashes  are  rather  injurious  than  useful  in 
the  coarser  cements. 

"The  black  powder,  of  charred  bones,  and  gray  bone-ashes 
have  nearly  the  same  effects  as  sorted  bone-ashes  have,  when  the 
powder  of  them  is  sorted  in  the  same  manner,  excepting  what  relates 
to  color. 


BONE  ASHES  IN  MORTAR. 


99 


'*  These  observations  on  bone-ashes  were  made  on  specimens  of  mor- 
tar laid  on  tiles,  and  small  pieces  of  incrustations  made  on  the  v/alls 
of  my  house,  and  on  the  fence-walls  behind  it.  But  they  v/ere  not 
confirmed  thoroughly,  until  a  comparison  was  made  between  large 
incrustations  laid  in  trying  aspects,  and  containing  bone-ashes, 
\vith  those  close  by  them,  of  my  best  mortar,  some  months  afterwards, 
when  I  discovered  the  difficulty  (expressed  in  the  fourteenth  section) 
of  making  extensive  incrustations,  in  certain  circumstances  so 
free  from  defects  as  the  smaller  ones  were,  which  I  had  made  at 
home. 

"By  the  analogy  of  bone-ashes  to  cinders,  or  ashes  of  other  bodies 
by  the  effects  of  them  in  my  experiments,  and  by  the  observa- 
tions I  have  made  on  houses  and  garden  walls  which  have  been 
fronted  or  entirely  stuccoed  with  my  cement,  I  have  been  led  into  the 
following  opinions,  concerning  the  agency  of  bone-ashes  in  calcareous 
cements : — 

"  The  mortar  which  contains  bone-ashes,  partakes  in  some  degree 
of  the  elasticity  and  sponginess  of  their  grains,  and  is  the  less  liitble 
to  crack  in  setting,  for  the  same  reason  that  sponginess  is,  in  any 
other  body,  and  effectual  preventive  of  fissures  in  drying,  or  because 
any  contraction  of  the  lime-paste,  in  consequence  of  the  exhalation 
of  its  w^ater,  is  combined  to  the  circuit  of  the  spongy  grains  compress- 
ed in  beating,  trowelling,  and  floating  the  cement,  and  is  thereby 
prevented  from  running  longitudinally  to  form  fissures.  The  same 
texture  of  bone-ashes,  contributes  to  this  effect,  or  causes  it,  upon 
other  principles,  which  are  less  exceptionable,  and  there  is  no  reason 
to  doubt  that  bone-ashes,  whose  grains  are  tubulated  in  all  possible 
directions,  which  greedily  imbibe  water,  and  emit  air,  and  which 
render  the  mortar  in  which  they  are  mixed,  manifestly  bibulous ;  fa- 
cilitate the  entry  of  acidulous  gas  into  the  cement,  and  that  this  mat- 
ter entering,  so  fast  as  the  water  exhales,  occupies  the  place  of  the 
water  in  the  cement,  and  by  preventing  the  contraction  of  it,  avoids 
fissures.    The  speedy  induration  of  the  cement  which  implies  a  quick 


100 


BONE  ASHES  IN  MORTAR. 


and  copious  accession  of  acidulous  gas,  according  to  our  opinion  and 
experience,  is  a  proof  of  this  agency  of  bone-ashes,  as  well  as  an  effect 
deducible  from  their  texture,  and  from  these  premises,  we  may  easily 
conceive  how  they  accelerate  the  setting  of  calcareous  incrustations, 
and  tend  to  secure  them  from  the  injuries  of  variable  weather. 

These  properties  of  bone-ashes  render  tbem  peculiarly  useful  in 
incrustations  made  within  doors,  on  principal  walls,  and  the  admix- 
ture of  them  in  half  the  quantity  of  the  lime,  or  in  a  greater  quantity, 
is  the  improvement  I  pointed  out  in  the  twentieth  section,  whereby 
the  damp  that  disfigures  the  common  incrustations  made  in  the  cir- 
cumstances there  described,  may  be  obviated  without  incurring  the 
expenses  of  lath-work. 

* '  Those  who  know  that  one-sixth  part  of  charred  bones,  or  about 
one-tenth  part  of  well-burned  bones,  is  phosphoric  acid,  may  have 
some  doubt  concerning  the  duration  of  a  cement  in  which  they  are 
mixed  in  large  quantity,  unless  they  consider  that  the  strength  of  the 
cement  does  not  depend  on  them,  and  that  it  is  impossible  for  the  phos- 
phoric acid  to  quit  the  lime  of  bone-ashes,  in  order  to  dissolve  the 
saturated  lime  of  the  cement.  Though  the  bone-ashes  should  perish 
in  a  century,  which  is  not  probable,  the  cement  is  not  likely  to  fail  on 
this  account,  provided  the  quantity  of  them  is  not  excessive. 

Thus  I  surmounted  the  difficulties  mentioned  in  the  fourteenth 
section,  and  made  my  best  calcareous  cement  applicable  in  all  cemen- 
titious  and  crustaceous  works,  external  or  internal,  without  inducing 
in  it  any  disagreeable  color  or  other  imperfection. 


101 


SPECIFICATION    OF    THE    AUTHOR'S  PATENT 
CEMENT. 

''To  ALL  TO  WHOM  THESE  PRESENTS  SHALL  COMB,  &C., 

"Now know  ye,  that  in  compliance  with  the  said  proviso,  I,  the 
said  Brindlet  Higgins,  do  hereby  declare  that  my  invention  of  a  water 
cement  or  stucco,  for  building,  repairing  and  plastering  walls,  and  for 
other  purposes,  is  described  in  the  manner  following  (that  is  to  say) : 
Drift  or  quarry  sand,  which  consists  chiefly  of  hard  quartoze,  flat- 
faced  grains  with  sharp  angles ;  which  is  the  freest,  or  may  be  most 
easily  freed  by  washing,  from  clay,  salts,  and  calcareous,  gypseous, 
or  other  grains  less  hard  and  durable  that  quartz  ;  which  contains  the 
smallest  quantity  of  pyrites  or  hea\^  metallic  matter,  inseparable  by 
washing,  and  which  suffers  the  smallest  diminution  of  its  bulk  in 
washing  in  the  following  manner,  is  to  be  preferred  before  any  other. 
And  where  a  coarse  and  a  fine  sand  of  this  kind,  and  corresponding 
in  the  size  of  their  grains  with  the  coarse  and  the  fine  sand  hereafter 
described,  cannot  be  easily  procured,  let  such  sand  of  the  foregoing 
quality  be  chosen,  as  may  be  sorted  and  cleansed  in  the  following 
manner. 

*'Let  the  sand  be  sifted  in  streaming  clear  water,  through  a  sieve 
which  shall  give  passage  to  all  such  grains  as  do  not  exceed  one-sixteenth 
of  an  inch  in  diameter,  and  let  the  stream  of  water  and  the  sifting  be 
regulated  so  that  all  the  sand  which  is  much  finer  than  the  Lynn  sand 
commonly  used  in  the  London  glass-houses,  together  with  clay  and 
every  other  matter  specifically  lighter  than  sand,  may  be  washed 
away  with  the  stream,  whilst  the  purer  and  coarser  kind  of  sand  which 
passes  through  the  sieve  subsides  in  a  convenient  receptacle,  and 
whilst  the  coarse  rubbish  and  rubble  remain  in  the  sieve  to  be  re- 
jected. 

**Let  the  sand  which  thus  subsides  in  the  receptacle  be  washed  in 


102 


IIIGGINS'S  PATENT. 


clear  streaming  water,  through  a  finer  sieve,  so  as  to  be  further 
cleansed  and  sorted  into  two  parcels :  a  coarser,  which  will  remain  in 
the  sieve,  which  is  to  give  passage  to  such  grains  of  sand  only  as  are 
less  than  one-thirtieth  of  an  inch  in  diameter,  and  which  is  to  be  saved 
apart  under  the  name  of  coarse  sand ;  and  a  finer,  which  will  pass 
through  the  sieve  and  subside  in  the  water,  and  which  is  to  be  saved 
apart  under  the  name  of  fine  sand. 

"Let  the  coarse  and  the  fine  sand  be  dried  separately,  either  in 
the  sun,  or  on  a  clean  iron  plate,  set  on  a  convenient  furnace,  in  the 
manner  of  a  sand-heat. 

**Let  lime  be  chosen,  which  is  stone-lime,  which  heats  the  most  in 
slaking,  and  slakes  the  quickest  when  duly  watered ;  which  is  the 
freshest  made,  and  closest  kept,  which  dissolves  in  distilled  vinegar 
with  the  least  effervescence,  and  leaves  the  smallest  residue  insoluble, 
and  in  this  residue,  the  smallest  quantity  of  clay,  gypsum  or  martial 
matter. 

**Let  the  lime  chosen  according  to  these  important  rules  be  put  in  a 
brass  wired  sieve,  to  the  quantity  of  fourteen  pounds.  Let  the  sieve 
be  finer  than  any  of  the  foregoing,  the  finer,  the  better  it  will  be . 
Let  the  lime  be  slaked  by  plunging  it  in  a  butt  filled  with  soft  water, 
and  raising  it  out  quickly,  and  suffering  it  to  heat  and  fume,  and  by 
repeating  this  plunging  and  raising  alternately,  and  agitating  the 
lime  until  it  be  made  to  pass  through  the  sieve  into  the  water,  and  let 
the  part  of  the  lime  which  does  not  easily  pass  through  the  sieve  be 
rejected,  and.  let  fresh  portions  of  the  lime  be  used,  until  as  many 
ounces  of  lime  have  passed  through  the  seive  as  there  are  quarts  of 
water  in  the  butt. 

*  *  Let  the  water  thus  impregnated  stand  in  the  butt  closely  covered, 
until  it  becomes  clear ;  and  through  wooden  cocks,  placed  at  different 
heights  in  the  butt,  let  the  clear  liquor  be  drawn  off,  as  fast  and  as 
low  as  the  lime  subsides,  for  use.  The  freer  the  water  is  from  saline 
matter,  the  better  will  be  the  lime-water  or  cementing  liquor. 

"Let  fifty-six  pounds  of  the  aforesaid  chosen  lime  be  slaked  by 


HIGGINS'S  PATENT. 


103 


gradually  sprinkling  on  it,  and  especially  on  the  unslaked  pieces,  the 
lime-water,  in  a  close,  clean  place.  Let  the  slaked  part  be  immediate- 
ly sifted  through  the  last  mentioned  fine  brass  wired  sieve.  Let  the 
lime  which  passes  be  used  instantly,  or  kept  in  air-tight  vessels,  and 
let  the  part  of  the  lime  which  does  not  pass  the  sieve  be  rejected. 
This  finer, richer  part  of  the  lime,  which  passes  through  the  sieve,  I 
caJl  purified  lime. 

*'Let  bone-ashes  be  prepared  in  the  usual  manner,  by  grinding  the 
whitest  burnt  bones,  but  let  it  be  sifted  so  that  it  be  much  finer  than 
the  bone-ashes  commonly  sold  for  making  cupels. 

*'  The  most  eligible  materials  for  making  my  cement  being  thus  pre- 
pared :  take  fifty-six  pounds  of  the  coarse  sand  and  forty-two  pounds 
of  the  fine  sand :  mix  them  on  a  large  plank  of  hard  wood,  placed 
horizontally,  then  spread  the  sand  so  that  it  may  stand  to  the  height 
of  six  inches,  with  a  flat  surface  on  the  plank ;  wet  it  with  the  lime- 
water,  and  let  any  superfluous  quantity  thereof,  which  the  sand  in  the 
condition  described  cannot  retain,  flow  away  off  the  plank.  To  the 
wetted  sand  add  fourteen  pounds  of  the  purified  lime,  in  several  suc- 
cessive portions,  mixing  and  beating  them  up  together  in  the  mean- 
time with  the  instruments  generally  used  in  making  fine  mortar ;  then 
add  fourteen  pounds  of  the  bone-ashes  in  successive  portions,  mixing 
and  beating  all  together.  The  quicker  and  the  more  perfectly  these 
materials  are  compounded,  and  the  sooner  the  cement  thus  formed  is 
used,  the  better  it  will  be. 

"  This  I  call  the  *  water  cement,'  coarse  grained,  which  is  to  be  applied 
in  building,  painting,  plastering,  stuccoing,  and  other  work,  as  mortar 
and  stucco  now  are,  with  this  difference  chiefly,  that  as  this  cement  is 
'  shorter '  than  mortar  or  common  stucco,  and  dries  sooner,  it  ought  to 
be  worked  expeditiously  in  all  cases,  and  in  stuccoing  it  ought  to  be 
laid  on  by  sliding  the  trowel  upwards  on  it ;  that  the  materials  used 
along  with  this  cement  in  building,  or  the  ground  on  which  it  is  to  be 
laid  in  stuccoing,  ought  to  be  well  wetted  with  the  lime-water  at  the 
instant  of  laying  on  the  cement,  and  that  the  lime-water  is  to  be  used 


104 


HIGGINS'S  PATENT. 


when  it  is  necessary  to  moisten  the  cement,  or  when  a  liquid  is  required 
to  facilitate  the  floating  of  the  cement. 

*' When  such  cement  is  required  to  be  of  a  finer  texture;  take 
ninety-eight  pounds  of  the  fine  sand,  wet  it  with  the  lime-water,  and 
mix  it  with  the  purified  lime  and  the  bone- ashes,  in  the  quantities  and 
in  the  manner  above  described,  with  this  difference  only,  that  fifteen 
pounds  of  lime  or  thereabouts,  are  to  be  used,  if  the  greater  part  of  the 
sand  be  as  fine  as  the  Lynn  sand. 

This  I  call  the  '  water  cement,'  fine  grained.  It  is  to  be  used  in 
giving  the  last  coating  or  the  finish  to  any  work  intended  to  imitate 
the  finer  grained  st-ones  or  stucco.  But  it  may  be  applied  to  all  the 
uses  of  the  coarser  grained  water  cement,  and  in  the  same  manner. 

When  for  any  of  the  foregoing  purposes  of  painting,  building,  &c., 
such  a  cement  is  required  much  cheaper,  and  coarser  grained,  then, 
much  coarser,  clean  sand,  or  well  washed  fine  rubble  is  to  be  provided^ 
Of  this  coarser  sand  or  rubble  take  fifty-six  pounds ;  of  the  foregoing 
coarse  sand,  twenty-eight  pounds ;  and  of  the  fine  sand,  fourteen 
pounds;  and  after  mixing  these  and  wetting  them  with  the  lime- 
water,  in  the  foregoing  manner,  add  fourteen  pounds  or  somewhat  less 
of  the  bone-ashes,  mixing  them  together  in  the  manner  described. 

"When  the  cement  is  required  to  be  white,  then  white  sand,  white 
lime  and  the  whitest  bone-ashes  are  to  be  chosen.  Gray  sand  and 
gray  bone-ashes  formed  of  half-burnt  bones,  are  to  be  selected  to  make 
the  cements  gray,  and  any  other  color  of  the  cement  is  obtained,  either 
by  choosing  colored  sand  or  by  the  admixture  of  the  necessary  quan- 
tity of  colored  talc,  in  powder,  or  of  colored  vitreous  or  metallic 
powders,  or  other  durable  coloring  ingredients  commonly  used  in 
paint. 

.  "To  the  end  that  such  a  water  cement  as  I  have  described  may  be 
made  as  useful  as  possible  in  all  circumstances,  and  that  no  person 
may  imagine  that  my  claim  and  right  under  these  ^  Letters  Patent  * 
may  be  eluded  by  divers  variations  which  may  be  made  in  the  foregoing 
process,  without  producing  any  notable  defect  in  the  cement,  and  to 


HIGGINS'S  PATENT.  105 

the  end  that  the  principles  of  this  art,  as  well  as  the  art  itself  of  mak- 
ing my  cement,  may  be  gathered  from  the  specification,  and  perpet- 
uated to  the  public,  I  shall  add  the  following  observations: — 

*'This,  my  water  cement,  whether  coarse  or  fine  grained,  is  applica- 
ble in  forming  artificial  stone,  by  making  alternate  layers  of  the 
cement  and  the.  flint,  hard  stone  or  brick,  in  molds  of  the  figure  of  the 
intended  stone,  and  by  exposing  the  masses  so  formed  to  the  open  air 
to  harden. 

"  When  such  cement  is  required  for  water  fences,  two-thirds  of  the 
prescribed  quantity  of  bone-ashes  are  to  be  omitted;  and  in  place 
thereof,  an  equal  measure  of  powdered  terras  is  to  be  used,  and  if  the 
sand  employed  be  not  of  the  coarsest  sort,  more  terras  must  be  added, 
so  that  it  shall  be  (by  weight)  one-sixth  part  of  the  weight  of  the 
sand.  When  such  a  cement  is  required  of  the  finest  grain,  or  in  a 
fluid  form,  so  that  it  may  be  applied  with  a  brush,  flint  powder,  or  the 
powder  of  any  quartoze  or  hard  earthy  substance  may  be  nsed  in  the 
place  of  sand,  but  in  a  quantity  smaller,  as  the  flint  or  other  powder 
is  finer,  so  that  the  flint  powder,  or  other  such  powder  shall  not  be 
more  than  six  times  the  weight  of  the  lime,  nor  less  than  four  times 
its  weight.  The  greater  the  quantity  of  lime,  within  these  limits, 
the  more  will  the  cement  be  liable  to  crack  by  quick  drying,  and 
vice  versa. 

"Where  such  sand  as  I  prefer  cannot  be  conveniently  procured,  or 
where  sand  cannot  be  conveniently  washed  and  sorted,  that  sand 
which  most  resembles  the  mixture  of  coarse  and  fine  sand  above  pre- 
scribed, may  be  nsed  as  I  have  directed,  provided  due  attention  is 
paid  to  the  quantity  of  lime,  which  is  to  be  the  greater,  as  the  sand  is 
the  finer,  and  vice  versa. 

"Where  the  sand  cannot  be  easily  procured,  any  durable  stony 
body,  or  baked  earth,  grossly  powdered,  and  sorted  nearly  to  the  sizes 
above  prescribed  for  sand,  may  be  used  in  the  place  of  sand,  measure 
for  measure,  but  not  weight  for  weight,  unless  such  gross  powder  be  as 
heavy,  specifically,  as  sand. 


106 


HIGGINS'S  PATENT. 


<<Sand  may  be  cleansed  from  every  softer,  lighter,  and  less 
durable  matter,  and  from  that  of  the  sand  which  is  too  fine,  by 
various  methods  preferable  in  certain  circumstances  to  that  which  I 
have  described. 

Water  may  be  found  naturally  free  from  fixable  gas,  silenite,  or 
clay ;  such  water  may  witliout  any  notable  inconvenience  be  used  in 
the  place  of  the  lime-water  ;  and  water  approaching  this  state  will  not 
require  so  much  lime  as  I  have  ordered,  to  make  the  cementing  liquor 
or  lime-water,  and  which,  sufficiently  useful  may  be  made  by  various 
methods  of  mixing  lime  and  water  in  the  described  proportions,  or 
nearly  so. 

When  stone-lime  cannot  be  procured,  chalk,  or  shell-lime  which 
best  resembles  stone-lime  in  the  characters  before  described,  may  be 
substituted,  except  that  fourteen  pounds  and  a  half  of  chaik-lime  will  be 
required  in  place  of  fourteen  pounds  of  stone-lime. 

^ '  The  proportion  of  lime  which  I  have  prescribed  above  may  be  in- 
creased without  inconvenience,  when  the  cement  or  stucco  is  to  be 
applied  where  it  is  not  liable  to  dry  quickly;  and  in  the  contrary 
circumstances,  this  proportion  may  be  diminished,  and  the  defect  of 
lime  in  quantity  or  quality  may  be  advantageously  supplied  by  caus- 
ing a  considerable  quantity  of  lime-water  to  soak  into  the  work,  in 
successive  portions  and  at  distant  intervals  of  time,  so  that  the  calcare- 
ous matter  thereof,  and  the  matter  attracted  from  the  open  air,  may 
fill  and  strengthen  the  work. 

The  powder  of  almost  every  well-dried  or  burnt  animal  substance 
may  be  used  instead  of  bone-ash,  and  several  earthy  powders,  especially 
the  micaceous  and  the  metallic,  and  elixated  ashes  of  divers  vegetables, 
whose  earth  will  not  burn  to  lime,  and  the  ashes  of  mineral  fuel,  which 
are  of  the  calcareous  kind,  but  will  not  burn  to  lime,  will  answer  the 
ends  of  bone-ash  in  some  degree. 

'*The  quantity  of  bone-ash  described  may  be  lessened  without  in- 
juring the  cement  in  those  circumstances  especially,  which  admit  ^he 
quantity  of  lime  to  be  lessened,  and  in  those  wherein  the  cement  is  not 


HIGGINS'S  PATENT. 


107 


liable  to  dry  quickly.  And  the  art  of  remedying  the  defects  of  lime 
may,  be  advantageously  practiced  to  supply  the  deficiency  of  bone- 
ash  especially  in  building  and  in  making  artificial  stone  with  this  ce- 
ment. 

B. — For  inside  work,  the  admixture  of  hair  with  this  cement 
is  useful. 

"The  excellency  of  my  cement  depends,  first,  on  the  figure,  size, 
and  purity  of  the  sand ;  secondly,  on  the  purity  of  the  lime,  obtained 
in  the  choice  of  lime-stone,  and  in  the  perfect  burning,  and  security 
in  preserving  it  from  the  air,  in  my  method  of  slaking,  and  in  the 
separation  of  heterogeneous  parts  ;  thirdly,  on  the  use  of  strong  and 
pure  lime-water,  in  the  place  of  common  water;  fourthly,  on  the  pro- 
portions of  sands,  lime-water  and  lime;  fifthly,  on  the  manner  of 
mixing  them ;  sixthly,  on  the  knowledge  of  ingredients  and  circum- 
stances which  are  injurious  or  useful ;  seventhly,  on  the  use  of  bone- 
ashes  of  determinate  size;  eighthly,  on  the  art  of  suiting  some 
of  these  to  the  several  purposes;  and  finally,  on  so  many  other 
particulars  as  render  it  very  diflicult  to  give  a  more  candid  specifica- 
tion in  the  usual  compass,  than  this  which  I  have  enrolled,  or  to  guard 
otherwise  against  evasions,  than  by  anticipating  them. 

"In  witness  whereof,  I,  the  said  B.  H.,"  &c. 

In  allusion  to  the  foregoing  specification,  the  author  (or  patentee) 
makes  the  following  remarks  :— 

"As  the  specification  of  these  letters-patent  comprehends  the  most 
useful  practical  instructions  deduced  from  the  foregoing  experiments 
and  observations,  and  may  serve  as  a  concise  recapitulation^  I  subjoin 
a  transcript  of  it. " 


108 


Experimental  Comparison  of  Chalk-lime  with  Stone-lime. 
Advice  to  Manufacturers  of  Chalk-lime  concerning  the 
Art  of  making  it  equal,  if  not  superior,  to  Stone-lime, 

FOR  the  purposes  OF  BuiLDERS,  SOAP-BOILERS.  AND  SuGAR- 
BAKERS. 

''All  the  authors  whom  I  have  consulted,  who  have  treated  of  ce- 
mentitious  buildings  and  of  lime,  from  the  time  of  Vitruvius,  who 
wrote  on  these  subjects  in  the  reign  of  the  Roman  emperor,  Titus,  or 
before  it,  down  to  the  present  hour,  and  all  the  artists  with  whom  I 
have  conversed,  agree  in  the  opinion  that  lime  prepared  from  the 
closest  lime-stone  makes  a  stronger  cement  than  that  which  is  made 
of  spongy  lime-stone,  and  that  the  lime  of  chalk  particularly  is  inca- 
pable of  acting  as  effectually  as  the  best  lime-stone,  in  cementitious 
works  or  incrustations,  which  are  exposed  to  the  weather. 

"  This  universal  and  undisputed  notion  had  great  influence  with  me 
in  the  course  of  my  experiments,  until  I  had  discovered  not  only  the 
fallacy  of  it,  but  the  grounds  which  gave  rise  to  it ;  both  which  I  shall 
now  expose,  in  the  pleasing  hope  of  rendering  great  service  to  many 
of  my  friends,  and  all  who  are  proprietors  of  chalk-pits,  or  are  obliged 
to  use  chalk-lime  in  their  buildings. 

"  The  experiments  already  mentioned  afforded  me  a  great  many 
opportunities  of  comparing  cements  made  of  lime  and  sand,  or  with 
those  and  other  ingredients  in  various  proportions,  and  differing  only 
in  the  kind  of  lime.  Jn  these  comparisons  I  could  not  perceive  that 
chalk-lime,  judiciously  prepared  and  used,  was  in  any  respect  inferior 
to  the  best  stone-lime ;  but  I  did  not  content  myself  with  these.  I 
made  a  great  number  of  cements,  with  the  sole  view  of  collecting  the 
respective  merits  of  these  kinds  of  lime,  in  small  and  great  incrusta- 
tions, in  masses  made  to  resemble  cut  stone,  in  all  exposures  and 
seasons  of  the  year ;  and  after  the  strictest  comparisons  of  those  which 
contained  lime  in  equal  quantities,  and  were  treated  alike  in  all  re- 
spects, I  was  thoroughly  convinced  that  my  chalk-lime  was  as  good 


CHALK-LIME  AND  STONE-LXME.  109 

for  any  purpose  of  this  kind  as  the  best  stone-lime  in  the  kingdom  ; 
for  I  nsed  the  well-burned  lime  of  Plymouth  stone,  which  I  reckon 
among  the  most  excellent  of  our  lime-stones. 

'  *  This  stone  loses  seven-sixteenths  of  its  weight  in  conversion  into 
lime,  and  becomes  as  white  as  chalk.  Chalk  loses  a  little  more  in  the 
perfect  burning.  Plymouth  lime  leaves  a  small  gypseous  residue  in 
the  solution,  described  in  the  tenth  page,  which  is  preferable  to  that 
directed  in  the  specification ;  chalk  lime  leaves  none.  Therefore,  the 
chalk  lime,  chemically  or  technically  tried,  appears  to  be  equal  if  not 
superior  to  stone-lime,  in  its  cementing  powers,  when  it  is  properly 
used. 

"The  prejudices  entertained  against  chalk-lime  may  be  traced  to 
three  sources.  The  first  is  that  which  is  mentioned  in  the  fourth  sec- 
tion. The  vulgar  criterion  of  the  due  preparation  of  lime  consists  in 
the  slaking ;  and  as  chalk  which  has  undergone  a  slight  calcination 
and  thereby  lost  only  a  part  of  its  acidulous  gas,  is  capable  of  slaking, 
by  reason  of  its  sponginess,  the  manufacturers  of  chalk-lime  content 
themselves  with  the  degree  of  calcination  which  renders  it  tracticable 
or  vendible,  and  thus  bring  it  into  disrepute. 

The  second  source  is  mentioned  in  the  fifth  section.  Chalk-lime 
imbibes  acidulous  gas,  during  its  exposure  to  the  air,  much  faster 
than  stone-lime,  and  is  consequently  more  impaired  or  worse,  at  the 
time  of  using  it  in  mortar,  than  stone-lime  kept  in  the  same  circum- 
stances. As  the  lime  may  be  greatly  injured  in  this  way,  without 
slaking  sensibly,  and  as  there  was  no  suspicion  or  measure  of  such  in- 
jury, beyond  what  the  slaking  afforded,  the  acquired  imperfection  of 
ehalk-lime  was  considered  as  the  very  nature  of  it.  In  our  foregoing 
remarks,  it  appears  that  a  pound  of  chalk-lime,  placed  in  the  quiescent 
air  of  a  chamber,  imbibes  two  ounces  and  a  half  of  acidulous  gas  in 
two  days ;  which  is  the  shortest  time  in  which  lime  is  usually  exposed, 
if  we  count  from  the  moment  of  its  being  red-hot  to  that  of  its  being 
mixed  in  mortar,  during  which  interval  it  is  in  the  state  of  ab 
sorption. 


110 


CHALK-LIME  AND  STONE-LIME. 


"The  third  source  I  have  discovered  in  the  structure  of  the  lime- 
kilns. The  cavity  of  a  lime-kiln  has  the  figure  of  a  truncated  cone, 
inverted.  When  the  charge,  consisting  of  lime-stone  and  fuel,  alter- 
nately stratified,  has  burned  for  some  time,  the  fuel  is  exhausted  at 
the  lower  narrow  extremity  of  the  cavity,  the  lime  in  this  part  cools, 
and  serves  as  a  grate  to  the  fuel  and  lime-stone  above  it,  which  con 
tinue  to  burn  briskly,  for  eighteen  hours  longer,  after  the  lime  beneath 
begins  to  cool.  Duiing  this  time,  the  last-mentioned  part  of  the  lime 
is  exposed  to  a  strong  current  of  air,  and  the  whole  charge  of  lime 
stands  in  the  like  current  of  air  until  the  lime  is  cooled,  or  with- 
drawn; which  in  common  practice  is  seldom  or  never  done  till 
the  sixtieth  or  seventieth  hour  after  the  combustion  of  the  fuel  com- 
menced. 

''The  injury  which  lime-stone  sustains  in  these  circumstances, 
which  I  have  often  imitated  in  my  laboratory,  is  not  great,  because 
this  lime  is  much  more  compact  than  the  chalk-lime.  But  when  we 
observe  that  the  best  pieces  of  chalk-lime  of  the  common  kilns,  and 
those  which,  after  beating  them  sufficiently,  I  had  left  in  the  fire- 
place, exposed  as  they  are  in  the  usual  process,  are  always  effervescent ; 
that  good  chalk-lime,  in  a  weaker  current  of  air,  imbibes  more  than 
three  ounces  of  acidulous  gas  into  each  pound  of  it,  in  two  days,  ac- 
cording to  our  former  experiment,  and  that  my  chalk-lime,  which  I 
remove  from  the  fire-place  as  soon  as  it  is  sufficiently  burned,  is  per- 
fectly non-effervescent ;  we  find  that  the  long  experienced  imperfec- 
tions of  fresh  chalk-lime  are  owing  more  to  the  faulty  construction  of 
the  kilns,  and  the  ignorance  of  the  manufacturer,  than  to  any  incapa- 
city of  chalk  to  yield  excellent  lime. 

"  The  means  of  preparing  chalk-lime  to  equal  stone-lime,  and  of 
making  the  best  stone-lime,  may  be  gathered  from  what  I  have  said, 
and  the  following  intimations  : — 

"The  kilns  are  to  be  made  broader  and  shallower  in  the  cavity 
which  receives  the  charge ;  the  circular  waU  enclosing  this  cavity,  is 
to  be  continued  tapering  upwards,  until  it  terminates  in  a  lofty  flue, 


CHALK-LIME  AND  STONE-LIME. 


Ill 


in  order  to  accelerate  the  combustion,  and  increase  the  heat  by  a  quick 
current  of  air,  to  be  regulated  by  opening  or  closing  the  doorway, 
which  is  to  be  left  in  the  circular  wall,  at  a  convenient  height  for  the 
introduction  of  the  charge.  The  massive  walls  of  the  lower  cone  are 
to  be  lined  with  fire-brick,  or  a  pyrous  stone  set  in  the  best  fire-loam, 
and  are  to  be  girded  with  iron.  The  fuel  is  to  be  stratified  with  the 
lime-stone,  or  chalk,  and  the  combustion  is  to  be  so  conducted,  that 
every  part  of  the  charge  shall  be  sufficiently  ventilated  and  heated, 
and  that  the  lowest  shall  remain  red-hot,  until  the  whole  is  well-burn- 
ed. Then  the  current  of  air  through  the  kiln  is  to  be  stopped  by 
closing  the  apertures  at  the  bottom,  or  the  red-hot  lime  is  to  be  re- 
moved out  of  it,  to  cool  in  quiescent  air,  until  it  is  fit  to  be  enclosed 
in  air-tight  vessels. 

"A  cask  of  chalk-lime  is  not  to  be  opened  until  the  moment  when 
the  workman  is  ready  to  slake  the  lime ;  and  the  greatest  expedition 
is  to  be  used  in  the  slaking,  in  making  the  mortar,  and  in  applying  it 
to  use.  By  this  treatment,  the  chalk-lime  will  answer  every  end 
of  the  best  stone-lime,  and  stone-lime  may  be  prepared  and  pre- 
served in  the  highest  perfection  which  the  nature  of  the  lime-stone 
can  admit. 

"The  manufacturer  of  chalk-lime  who  adopts  this  plan  will  profit 
by  it,  for  good  lime  is  not  only  better,  but  goes  further  in  building, 
than  bad  lime ;  good  chalk-lime  will  answer  the  purposes  of  the  soap- 
boiler, in  half  the  quantity  which  they  use  of  common  chalk-lime,  the 
greater  part  of  which  serves  only  to  waste  their  lees,  and  clog  their 
vats ;  and  the  sugar-bakers  will  not  hesitate  about  the  price  of  good 
chalk-lime,  when  they  find  that  it  is  totally  soluble  in  pure  water,  and 
introduces  no  selenitic  matter  into  the  sugar.  The  exportation  of 
lime  to  the  West  India  islands  will  be  a  further  incitement  towards 
the  improvements  which  I  have  s%gested,  when  they  understand  the 
principles  by  which  fee,  duly  admmm^red facilitates,  hut  injudicious^ 
ly  used,  impedes  the  granulation  of  tRe  saccharine  parts  of  their  cane 
juices."  '  ■ 


112 


POZZOLANA  OR  PUZZOLANA. 

"This  mineral  being  a  very  essential  ingredient  in  the  composition 
of  hydraulic  cement,  a  brief  account  of  it  here,  may  not  be  considered 
out  of  place,  or  uninteresting. 

Pozzolana  is  a  greyish  kind  of  earth,  much  used  in  Italy  and  else- 
where, for  building  under  water—  the  best  variety  of  which  is  found 
about  Pozzuola,  (Puteoli,)  Cumaj,  Baias,  &c.,  in  the  kingdom  of 
Naples  ;  and  from  the  former  of  which  places  it  derives  its  name. 

"The  mineral,  of  itself,  is  a  pale  greyish  powder,  composed  of 
particles  so  very  minute,  as  to  escape  distinction  even  by  the  aid  of 
powerful  glasses,  and  when  viewed  through  a  microscope  appear  only 
a  loose,  fine  irregular  powder,  and  containing  small  quantities  of  talc 
spangles,  and  when  mixed  with  water  in  a  glass  vessel,  and  well- 
shaken  up,  leaves  a  white  muddiness  in  it,  which  requires  a  long  time 
to  subside ;  and  when  wetted  with  sea-water,  immediately  dries  into 
a  firm,  compact  mass,  similar  to  stone,  hence  its  value  for  marine 
works ;  it  will  do  the  same  when  mixed  with  fresh  water,  but  not  in 
80  great  a  degree. 

"Mixed  with  lime,  Pozzohna  makes  the  best  possible  mortar,  it 
hardens  and  petrifies  in  water. 

"  The  ancients  were  well  acquainted  with  this  substance,  and  its 
properties,  and  employed  it  extensively  in  the  construction  of  moles, 
piers,  &c.  of  bridges  and  all  works  exposed  to  direct  contact  with  sea- 
water,  or  subject  to  saline  atmosphere  or  impregnation.  Vitruvius, 
Pliny,  De  Lorme,  &c.,  set  great  value  on  it,  and  the  latter  is  reported 
to  have  used  it  largely  in  France.  Some  have  considered  it  to  be  of 
an  aluminous  and  sulphurous  nature. 

"It  is  said  to  have  been  first  no^ed  on  the  sea-shore  of  its  native 
place,  where  having  drifted  do\^^om  the  hills  by  the  force  or  action 
of  the  wind,  aided  by  the  law  ^Pavitation,  or  by  the  mountain  tor- 
rents, it  lodged  on  the  beach  or  sea-side,  and  becoming  mixed  with 


POZZOLANA. 


113 


the  sea-water,  dissolved,  and  speedily  acquired  extreme  induration 
and  solidity,  so  much  so  as  to  be  by  many  mistaken  for  masses  of 
Dative  stone. 

*'The  remarkable  property  which  it  possesses  of  coalescing  so 
quickly  with  water,  is  probably  owing  to  its  having  in  its  composition 
a  large  proportion  of  a  certain  earth  very  common  on  the  sides  of 
hills  throughout  Italy,  and  known  to  the  ancients  by  the  name  of 
gypsum  tymphiacum,  and  by  the  moderns  as  calx  nativa,  and  which 
possesses  the  quality  of  forming  a  kind  of  plaster,  without  being 
burnt. 

*^Puzzolana  is  also  found  in  other  parts  of  Italy  than  those  before 
enumerated,  as  Viterbo,  Bologna,  &c.,  and  frequently  in  the  vicinity 
of  burning  mountains,  from  which  it  has  been  ejected  in  the  form  of 
ashes — in  the  crater  or  belly  of  which  volcanoes  it  had  been  previously 
burnt  or  calcined;  and  which  fact  will  reasonably  and  satisfactorily 
account  for  its  highly  cementitious  properties  (in  its  native  state) 
without  further  preparation.  It  is  said  to  exist  in  large  quantities, 
sometimes  covering  the  face  of  the  country,  and  even  whole  districts 
to  a  considerable  depth ;  and  it  is  sometimes  found  in  small  detached 
pieces  of  an  earthy  and  porous  texture ;  classed  by  mineralogists  under 
the  genus  "lava,"  and  is  considered  a  volcanic  product. 

"  It  is  magnetic,  and  readily  melts  stone  into  a  dark  slag;  it  quickly 
hardens  when  mixed  with  one-third  of  its  own  weight  of  lime  and 
water,  forming  a  cement  more  durable  under  water  than  any  other 
yet  known. 

''Upon  analysis  it  has  been  found  to  contain  the  following  com- 
ponents, viz., (out  of  one  hundred  parts, )from  fifty-five  to  sixty  of 
siliceous  earth,  twenty  of  argillaceous,  five  or  six  of  calcareous,  and 
from  fifteen  to  twenty  of  iron.  This  last  constituent  is  thought  to  be 
the  principal  cause  of  its  peculiar  property  of  hardening  under  water  . 
The  iron  decomposes  the  water,  thus  producing  in  a  short  time  a  new 
compound. 

Another  examination  of  a  specimen  of  puzzolana  gave  the  follow 


114 


ARTIFICIAL  PUZZOLANAS. 


ing  results:  44*5  of  silica,  15-0  alumina,  8*8  lime,  4*7  magnesia 
1*4  potash,  4*1  soda,  12  oxide  of  iron  and  bitumen,  and  9*2  water  iu 
100  parts. 

"The  Greeks  were  not  acquainted  with  this  substance,  and  the 
Romans  had  in  this  respect  a  great  advantage  over  them,  on  account 
of  the  solidity  it  imparted  to  their  buildings.  When  used  for  struc- 
tures in  or  under  water,  the  Romans  mixed  (according  to  Vitruvius) 
two  parts  of  Pozzolana  to  one  of  mortar.  The  ruins  of  edifices  near 
Baiae  attest  the  solidity  of  this  cement. 

**Puzzolana  was  called  by  the  Romans  ^  terra  puteolana^  from  the 
place  where  it  was  chiefly  obtained,  and  was  employed  by  them  with 
great  advantage  in  the  construction  of  their  pubUc  ways  at  Rome, 
and  its  vicinity. 

"Artificial  puzzolana  is  made  by  reducing  to  a  red  heat,  three 
parts  of  clay  to  one  of  slaked  lime  by  measure. 

"A  species  of  puzzolana  has  been  found  in  England  and  France, 
but  it  is  not  equal  in  quality  to  the  Italian. 

Puzzolanas  are  either  natural  or  artificial,  the  former  are  found  in 
situations  which  have  been  acted  upon  by  subterraneous  heat,  such  as 
is  contained  in  volcanos,  &c.  They  all  consist  of  silex,  alumina,  oxide 
of  iron,  and  a  little  lime ;  the  proportions  of  which  greatly  vary  in 
different  specimens,  the  silex  or  clay,  in  all  cases,  predominating, 
while  the  lime  and  iron  are  sometimes,  though  rarely,  wanting. 

"The  scoria  of  forges  and  furnaces,  broken  pottery,  and  pulverized 
brick  or  tile,  are  artificial  substances  analogous  to  puzzolanas.  One 
class  of  puzzolanas,  containing  a  large  portion  of  clay  or  argil,  resist 
the  action  of  sulphuric  acidf  another  class,  with  a  less  proportion  of 
clay,  readily  dissolve  with  this  acid,  abandon  the  clay,  which  imme- 
diately separates  and  subsides. 

"  Since  the  quality  of  natural  hydraulic  lime  depends  on  the  mixture 
of  various  ingredients,  with  only  a  certain  proportionate  quantity  of 
3lay,  combined  with  heat,  it  is  natural  to  suppose  that  an  artificial 
mixture  of  the  like  materials  submitted  to  heat,  would  produce  a 


ARTIFICIAL  PUZZOLANAS. 


115 


compound  of  equal  efficacy.  Experience  has  abundantly  confirmed 
this  opinion,  and  it  is  now  known  that  an  artificial  hydraulic  lime 
may  be  prepared  in  almost  any  place,  at  a  moderate  price,  and  equal 
to  the  natural. 

An  artificial  puzzolana  is  made  by  heating  of  slaked  lime,  one 
part  to  three  of  clay,  and  keeping  them  at  a  red  heat  for  several  hours ; 
after  which  cover  the  top  of  the  kiln  with  sand  or  earth,  and  when 
cool,  pack  it  up  close  in  casks  for  use. 

**It  is  well  known  that  puzzolana  in  itself  has  no  cementing  prop- 
erties, having  been  found  upon  analysis  to  consist  of  the  same  compo- 
nent parts  as  the  colored  clays  of  nature,  that  is,  chiefly  of  silica  and 
alumina,  with  a  small  portion  of  the  metallic  oxides,  and  sometimes 
with  a  little  lime  ;  but  when  mixed  with  the  weaker  hydraulic  limes, 
or  even  with  common  lime,  it  constitutes  a  hydraulic  mortar,  that 
sets  under  water,  but  more  slowly  than  either  the  natural  or  artificial 
water-cements. 

John  Smeaton,  C.  E.,  who  erected  the  Eddystone  lighthouse  in 
the  English  Channel,  is  accredited  as  having  been  the  first  to  bring 
puzzolana  into  public  notice  in  England,  and  used  it  extensively,  both 
in  a  pure  state  and  also  mixed  with  Watchet  or  Aberthaw  lime,  and 
other  hydraulic  ingredients  in  the  construction  of  that  far-famed  struc- 
ture, and  also  made  several  experiments  upon  its  peculiar  properties. 

*'Mr.  Stevenson,  C.  E.,  also  employed  puzzolana,  with  a  mixture 
of  Aberthaw  lime  and  sand,  at  the  building  of  the  Bell  Eock  light- 
house, opposite  to  the  mouth  of  the  river  Tay  (Scotland) ;  his  propor- 
tions were  one  measure  of  slaked  lime-powder,  one  measure  of  puzzo- 
lana, one  measure  of  sand. 

The  most  ancient  sort  of  artificial  puzzolana  is  composed  of  brick- 
dust  or  tile-dust,  or  fragments  of  broken  pottery  ground  to  powder,  and 
being  mixed  with  lime,  produced  a  cement  more  impervious  to  water 
than  common  mortar  made  of  lime  and  sand,  and  which  in  all  probabil- 
ity was  in  common  use  in  the  time  of  the  Romans,  as  may  be  inferred 
from  some  passages  of  Vitruvius.  Puzzolana  and  brick-dust  not  only 


116    EXPERIMENTS  ON  AETIFICIAL  PUZZOLANA. 


resemble  each  other  in  appearance,  but  chemistry  prove  that  they  con- 
tam  the  same  component  parts,  both  being  originally  clays,  and  both 
being  moderately  calcined  or  burned,  the  one  by  volcanic  agency,  and 
the  other  in  a  kiln  or  clamp. 

This  primitive  sort  of  artificial  puzzolana  has  been  in  constant 
use  from  time  immemorial  in  the  south  of  Europe,  and  especially  in 
France,  where  the  term  '  cement '  has  been  applied  to  it,  which,  when- 
ever it  occurs  in  any  French  work  on  practical  architecture,  may  be 
taken  invariably  and  exclusively  to  signify  brick  or  tile-dust  mixed 
with  lime  for  the  purpose  of  forming  a  hydraulic  mortar,  but  which 
term  has  been  supplanted  by  M.  Vicat,  who  employs  the  phrase  *  arti- 
ficial puzzolana,'  which  is  now  almost  universally  adopted  by  modern 
authors. 

**The  Dutch,  to  whom  hydraulic  mortars  have  long  been  known, 
and  of  great  importance,  accustom  themselves  to  burn  a  clay  found 
under  the  sea  of  their  coast,  for  the  purpose  of  forming  an  artificial 
puzzolana,  which  is  said  to  be  a  close  and  good  imitation  of  the  natu- 
ral '  trass  *  of  Andernach  on  the  Rhine,  and  which  is  often  sold  and 
exported  as  such. 

A  series  of  experiments  undertaken  by  Col.  Pasley  (at  Chatham) 
on  artificial  puzzolana,  produced  the  following  restdts: — 

1st.  That  the  calcined  blue  clay  of  the  river  Medway  forms  bet- 
ter artificial  puzzolana  than  the  calcined  brown  pit  clay  of  Up- 
nor,  but  in  its  water-setting  properties  it  is  rather  inferior  to  natural 
puzzolanas. 

2d.  That  the  finest  clays  make  the  best,  and  pounded  bricks  the 
worst,  artificial  puzzolana. 

"  3d.  That  no  hydraulic  mortar,  except  cement,  will  set  on  the 
outside  of  walls,  exposed  to  the  violent  action  of  the  water. 

«<4th.  That  puzzolana  mortars,  as  well  as  those  of  the  strongest 
hydraulic  limes,  require  to  be  protected  by  cement  in  all  the  external 
joints. 

*<5th.  That  the  mortar  of  walls  built  with  weak  hydraulic  limes 


ANALYSIS  OF  TRASS  AND  PUZZOLANA.  117 


;vill  not  set  nnder  water,  unless  improved  by  puzzolana  as  well  as  be- 
ing guarded  aU  round  with  cement 

ANALYSIS  OP  TRASS  AND  PUZZOLANA. 

"The  chemical  component  parts  of  Trass  and  Puzzolana  are  so 
nearly  alike,  that  the  one  cannot  possess  any  property  not  belonging 
to  the  other,  though  it  may  be  in  a  lesser  or  greater  degree,  but  ii; 
ought  to  be  understood,  that  the  puzzolanas  and  trasses  even  of  the 
same  locality,  may  somewhat  differ  from  each  other  in  the  proportions 
of  their  component  parts,  and  those  from  different  localities  still  more^ 
and  the  same  remark  will  apply  to  hydrauHc  limes  and  water  cements^ 
The  trass  used  by  Mr.  Stevenson  on  commencing  the  Bell-rock  light" 
house,  for  want  of  puzzolana,  is  stated  to  have  contained  in  100  parts^ 
silica  57,  alumina  28,  lime  6*5,  and  oxide  of  iron  8*5. 

"The  puzzolana  used  by  him  for  the  same  lighthouse  contained, 
silica  55  parts,  alumina  20,  lime  5,  and  oxide  of  iron  20. 

"The  following  shows  the  component  parts  of  the  trass  and  puz 
zolana  used  by  General  Treussart  at  Strasburgh,  as  analyzed  by  M. 
Berthier : — 


TEASS, 

PUZZOLANA. 

445 

Alumina, 

120 

150 

88 

Magnesia, 

10 

47 

Oxide  of  Iron, 

50 

120 

Potassa, 

70 

14 

10 

40 

Water,     .      ,      ,  , 

96 

92 

*  952 

996 

118 


NOTES  FROM  THE 
LATE  GENERAL  SIR  C.  W.  PASLEY'S  (K.C.B.,  R.E.) 
WORK  ON  LIMES. 

Pure  limes  are  those  which  consist  entirely  of  caroonate  of  lime ; 
that  is,  lime  combined  with  carbonic  acid  gas  or  fixed  air,  in  the  pro- 
portion of  five  parts  by  weight  of  the  former  and  four  of  the  latter — 
they  are  all  white,  such  as  pure  chalk ;  the  Carrara  marbles  used  by 
statuaries  being  the  purest  limestone  in  nature,  and  are  entirely  soluble 
in  muriatic  or  nitric  acid,  which  expels  the  carbonic  acid  gas  with 
great  effervescence  which  is  a  certain  test  of  their  properties  and 
character ;  and  when  chalk  or  white  marble  is  exposed  to  a  strong  red 
heat,  as  in  a  lime-kiln,  the  carbonic  acid  gas  is  driven  off  and  the 
stone  is  converted  into  quick-lime,  and  ia  which  state,  if  a  piece  be 
dropped  into  either  of  the  above  mentioned  acids  (diluted),  no  effer- 
vescence will  occur  ;  the  quick-lime,  when  slaked  with  water,  speedily 
falls  to  pieces  into  a  fine  powder  with  great  heat,  and  is  then  termed 
*  hydrate  of  lime, '  in  which  condition  it  is,  by  admixture  with  certain 
proportions  of  sand  and  water,  converted  into  building  mortar.  Sixty- 
three  pounds  of  pure  native  chalk  will  produce,  upon  an  average,  35 
pounds  of  lime,  and  when  slaked  with  a  proper  quantity  of  water  will 
occupy  a  space  of  about  1  §  cubic  foot.  A  cubic  foot  of  solid  chalk 
weighs  95  pounds.  The  process  of  slaking  wiU  increase  the  weight  of 
a  cubic  foot  of  lime  from  35  to  about  50  pounds,  or  in  the  proportion 
of  7  to  10.  The  carbonic  acid  gas  driven  off  by  the  process  of  burning 
the  Ume-stone  is  gradually  recovered  after  slaking  the  lime. 

Thirty-five  pounds  of  fresh-burnt  chalk-lime,  mixed  with  3  \ 
cubic  feet  (87  pounds  to  the  cubic  foot)  of  river  sand,  and  about  1  J 
cubic  foot  of  water,  produces  about  3  \  cubic  feet  of  good  mortar,  or 
one-fourth  of  a  cubic  foot  less  bulk  than  the  sand  alone  previously  oo- 
cupied,  which  is  owing  to  the  solidifying  effect  of  the  water  upon  the 
dry  materials. 


NOTES,  &c. 


119 


Pounded  quick-lime  measures  less,  and  slaked  powder  of  lime 
measures  more  in  bulk  than  it  originally  occupied. 

*'Pure  carbonates  of  lime  are  suitable  for  mortar  to  be  used  in  dry 
situations  or  for  inside  work,  but  are  unsuited  for  wet  or  damp  posi- 
tions, and  consequently  quite  unfit  for  hydraulic  mortar.  In  works 
which  are  much  exposed  to  damps  or  to  occasional  floodings,  when 
iime-mortar  is  chiefly  to  be  employed,  it  is  a  good  method  to  p(»nt  all 
the  external  joints  with  Koman  or  hydraulic  cement. 

Walls  built  with  chalk-limes  are  most  liable  to  *  settle*;  those 
built  with  hydraulic  limes  settle  less,  and  such  as  are  built  with  ce- 
ment, not  at  all." 

OF   WATEE   LIMES   OR   HYDRAULIC  LIMES. 

"  These  are  composed  of  carbonate  of  lime,  generally  mixed  with 
silica,  alumina,  and  the  oxide  of  iron,  and  with  frequent  indications 
of  other  matter ;  if  the  carbonate  of  lime  be  removed  the  residuary 
parts  are  of  a  clayey  nature,  from  which  fact  the  occasional  term  of 
(vgiUaceous  lime-stones  is  derived ;  they  possess  the  peculiar  and  valu- 
able property  of  setting  in  wet  or  damp  situations,  and  are  therefore 
very  useful  in  the  construction  of  marine  works,  and  dock  and  river 
walls,  especially  when  protected  in  front  with  such  superior  cements  as 
puzzolana,  trass,  or  English  cement. 

Of  all  the  English  lime-stones  the  Blue  Lias  stones  are  reckoned 
the  best  and  strongest ;  they  are  found  in  the  British  Channel,  also 
near  Watchet  in  Somersetshire,  at  Aberthaw  in  Glamorganshire 
(Wales),  and  at  Lyme  Regis  in  Dorsetshire.  The  former  of  these  was 
mixed  with  puzzolana  and  used  by  Smeaton  in  the  construction  of  the 
Eddystone  lighthouse. 

The  Dorking  or  Mersham  lime,  and  also  the  Hailing  lime  (Eng- 
land), are  much  valued  as  hydraulic  cements,  especially  the  former, 
and  are  much  employed  in  London. 

All  the  water  lime-stones  are  of  a  bluish  gray,  or  brown  color, 
which  they  derive  from  oxide  of  iron,  and  are  usually  termed  stone- 


120 


NOTES,  &c. 


limes,  in  contradistinction  to  chalk-limes.  Colored  chalks  are  com- 
monly termed  gray  chalks ;  they  are  usually  free  from  flints,  and  are 
more  or  less  possessed  of  hydraulic  properties. 

"  Most  of  the  water  lime-stones,  when  burned  into  quick-lime,  so 
as  to  expel  the  carbonic  acid  gas,  are  of  a  yellowish  or  light  brown 
color,  so  that  any  calcareous  stone,  which,  after  calcination,  assumes 
a  kind  of  buff  color,  may  be  considered  to  have  hydraulic  properties. 
Water  limes  will  not  bear  so  much  sand  as  common  chalk  lime. 

Three  measures  of  sand  and  one  of  Dorking  or  Hailing  lime  make 
a  good  mortar,  but  blue  lias  stone  lime  requires  only  twice  its  meas- 
ure of  sand  to  produce  good  mortar. 

"  Magnesian  lime-stones  possess  some  amount  of  hydraulic  proper- 
ties, but  do  not  make  a  good  water  lime  or  water  cement.* 

WATER  CEMENTS,  USUALLY  TERMED  ROMAN  CEMENTS.  * 

"  The  best  varietiesof  these  are  produced  from  the  isle  of  Sheppy,  Har- 
wich, Yorkshire,  &c.,  and  they  differ  chemically  from  water  limes  in 
having  less  carbonate  of  lime,  and  more  silica  and  alumina,  and  prac- 
tically, in  not  slaking  with  mortar  unless  previously  pulverized ;  that 
powder  balls  made  of  these  cements,  calcined  and  mixed  with  water, 
will  not  swell  and  burst,  but  will  set  not  only  in  air  but  under  water, 
even  if  instantly  immersed ;  and  that  these  cements  are  always  weak- 
ened by  the  addition  of  sand ;  and  also  in  the  necessity  for  their  im- 
mediate use  after  being  mixed,  before  they  begin  to  heat,  or  they  must 
be  thrown  away,  as  they  will  not  bear  to  be  re-mixed." 

ON  ANALYSING  LIME-STONES,  AND  TESTING   THEIR  SEVERAL 
PROPERTIES. 

A  Stone  supposed  to  be  a  water  cement,  ought  to  be  of  a  bluish 
gray,  or  brown,  or  some  darkish  color,  as  white  indicates  pure  lime- 

•  Note.  The  propertiea  of  the  Sheppy  cement  were  first  discovered  by  Mr, 
Parker,  who  took  out  a  patent  for  it  under  the  name  of  '  Roman  Cement,*  but  it 
is  better  known  as  Parker's  cement.  Mr.  Frost  discovered  the  Harwich  cement, 
and  Mr.  Atkinson  (architect)  that  obtained  from  Yorkshire. 


ANALYSIS  OF  CEMENTS. 


121 


stone  or  gypsum.  From  their  containing  silica  and  alumina,  which 
are  the  component  parts  of  clay,  the  natural  cement  stones,  on  being 
touched  with  the  tongue,  indicate  sensibly  the  presence  of  clay,  which 
is  also  detected  by  the  smell  after  wetting  them.  They  only  dissolve 
partially  in  diluted  acids,  having  a  more  copious  sediment  than  any 
of  the  lime-stones. 

' '  The  first  test,  therefore,  is  to  pour  a  little  diluted  muriatic  or 
nitric  acid  into  a  glass,  and  drop  a  fragment  of  the  stone  into  it.  If 
no  action  takes  place^  it  is  neither  a  lime-stone  nor  cement ;  but  if  it 
effervesce  and  fall  to  pieces  with  a  muddy  sediment,  it  is  probably  a 
water-cement.  To  ascertain  this  point,  break  the  stone,  if  necessary, 
into  compact  fragments,  not  exceeding  one  inch  and  a  half  in  thick- 
ness, and  put  two  or  three  of  these  into  a  common  fire-place,  first 
heating  them  gradually,  that  they  may  not  burst  into  too  many 
small  pieces,  and  keep  them  exposed  to  a  full  red  heat  for  about  three 
hours.  At  the  end  of  this  time,  take  one  of  your  specimens  out  of  the 
fire,  and  put  a  small  fragment  of  it  into  a  glass  of  diluted  muriatic 
or  nitric  acid.  When  the  stone  is  burned  enough,  that  is,  when  all 
the  carbonic  acid  gas  has  been  driven  off  by  the  heat,  no  effervescence 
will  take  place  in  the  acid.  A  moderate  effervescence  will  show  that 
it  is  a  little  under-burned,  but  violent  effervescence  will  prove  that  it 
is  very  imperfectly  burned,  and  it  should  therefore  be  put  into  the  fire 
again. 

Care  must  be  taken  not  to  over-burn  the  cement,  which  would 
always  injure  if  not  entirely  spoil  it ;  this  fact  may  be  known  by  its 
changing  to  an  unnatural  dark  color,  and  which  is  a  proof  of  incipient 
vitrification  ;  for,  by  excess  of  heat,  all  the  natural  cement  stones  may 
be  fused  into  a  dark-colored  glassy  substance  resembling  the  volcanic 
product  called  obsidian. 

*'If,  therefore,  the  calcined  cement  stone  does  not  effervesce  with 
acids,  and  if  at  the  same  time  its  proper  color  be  not  changed  to  a 
darker  one  on  taking  it  out  of  the  fire,  it  will  prove  that  it  is  properly 
burned. 

6 


122 


ANALYSIS  OF  CEMENTS. 


**  The  next  process  is  to  pound  the  perfectly  calcined  specimens  to 
an  impalpable  powder,  which  state  is  ascertained  by  its  not  feeling 
gritty  when  rubbed  between  the  fingers  and  thumb.  This  is  an  im- 
portant condition  of  natural  and  artificial  cements,  for  their  properties 
are  much  deteriorated  by  not  being  finely  powdered  after  calcination. 
You  must  then  proceed  to  mix  a  small  quantity  of  the  powder  with  a 
moderate  quantity  of  water,  upon  a  slate  or  slab,  into  a  paste,  with  a 
spatula  or  knife,  and  then  form  it  into  a  ball  by  turning  it  between 
the  palms  of  the  hands,  when  it  will  become  warm,  and  if  it  be  a  good 
water-cement  it  will  not  only  set  or  harden  in  the  heating,  but  if 
put  into  a  vessel  of  water  will  become  more  indurated.  Good  ce- 
ment will  harden  under  water,  even  if  put  in  while  wet,  but  it  is 
better  to  wait  and  let  it  cool  a  little  before  you  put  it  in. 

The  setting  of  these  cement  balls  will  be  greatly  retarded  by  using 
an  excess  of  water  in  their  mixture,  the  best  proportion  of  which  ap- 
pears to  be  one-fourth  part  of  water  to  one  of  cement.  During  the 
process  of  setting,  they  always  throw  out  a  vapor  so  long  as  the  heat 
continues. 

*  ^  The  Sheppy  cement  stone  is  usually  found  in  boulders  or  round 
nodules,  and  when  dry  is  of  a  light  brown  color. 

The  Harwich  cement  stone  is  obtained  in  larger  masses,  and  is 
of  a  dark  bluish  brown  color.  When  properly  burned,  the  former  is 
of  a  light  brown,  and  the  latter  of  nut  brown  color.  When  the  cal- 
cined powder  of  each  is  mixed  with  water  for  use,  both  mixtures  are 
brown,  but  the  former  is  much  lighter  than  the  latter,  which  approaches 
to  blackness. 

Since  cement  from  the  kiln  will  not  slake  even  with  water,  much 
less  by  the  action  of  the  air  alone,  it  might  be  preserved  for  a  long 
time  in  a  dry  room  as  I  have  proved  by  experiment ;  but  calcined  ce- 
ment being  useless  until  pulverized,  which  process  is  always  performed 
by  the  manufacturer  in  a  mill,  in  which  state  water  and  the  atmo- 
sphere is  enabled  to  act  upon  it. 

Calcined  cement  powder,  when  mixed  up  for  use,  recovers  (like 


AiN^ALYSIS  OF  CEMENTS. 


123 


the  lime  mortars)  in  time  the  whole  of  the  carbonic  acid  gas,  pre 
viously  thrown  off  by  the  fire,  and  is  brought  back  to  its  original  chemi- 
cal state.  And  old  cements  and  mortars  if  re-burnt,  calcined,  and 
pulverized  to  powder,  will  produce  a  material  nearly  as  good  as  from 
the  natural  stone. 

' '  Cement  powder  exposed  to  the  air,  especially  if  damp,  also  gradu- 
ally recovers  the  carbonic  acid  gas,  and  becomes  injured  and  eventually 
spoiled ;  for  which  reason  it  is  always  kept  in  tight  casks  or  bags,  but 
when  the  cement  becomes  damaged  or  stale,  it  may  be  recovered  or 
converted  into  good  cement  by  re-burning  it,  the  practicability  of 
which  may  be  ascertained  by  burning  some  stale  cement  powder  in  a 
crucible,  in  a  common  fire-place ;  but  if  any  considerable  quantity 
should  be  required  to  be  restored,  it  must  be  first  mixed  up  with  water 
into  balls  or  convenient  sized  lumps,  and  allowed  .sufficient  time  to 
set,  or  harden  before  being  re-burnt.  If,  however,  the  cement-powder 
should  be  too  stale  for  this  purpose,  let  a  small  portion  of  fine  clay, 
not  exceeding  one-tenth  part  (by  measure),  be  added  to  it,  in  making 
these  lumps,  which  will  cause  them  to  hold  together  in  the  kiln,  with- 
out materially  injuring  the  quality  of  the  cement. 

''The  most  powerful  water  cements  are  like  limes,  partially  decom- 
posed by  and  soluble  in  water  when  first  prepared  for  use,  but  the  in- 
jury is  too  insufficient  to  affect  the  solidity  of  structures  in  which  it  is 
employed. 

"  Cement,  soon  after  it  is  mixed  or  applied,  throws  out  an  efflores- 
cence at  first,  as  is  observable  in  the  fronts  of  buildings,  when  first 
stuccoed  therewith,  and  is  considered  a  criterion  of  good  quality. 
This  efflorescence,  when  viewed  in  the  sun  or  a  strong  artificial  light, 
presents  the  appearance  of  bright  crystals. 

"Whilst  water  cements,  and  water  limes  are  analogous  in  their 
component  parts,  and  general  properties,  there  is  great  distinction 
between  them  for  the  purposes  of  hydraulic  architecture,  inasmuch  as 
the  settmg  process  at  the  surface  comes  so  much  sooner  to  perfection 
in  the  former  than  m  the  latter,  that  the  water  which  after  this  period 


124 


ANALYSIS  OF  CEMENTS, 


ceases  to  act  perceptibly  upon  either,  has  not  time  to  irjure  the  ex- 
ternal joints  of  the  cement,  while  it  makes  a  considerable  impression 
upon  the  lime ;  in  this  consists  the  chief  difference  between  them,  and 
it  constitutes  their  relative  use  and  value. 

"  There  are  two  properties  of  cement  which  ought  to  be  fully  under- 
stood. 1st.  That  it  only  sets  rapidly  when  made  up  in  small  parcels 
or  thin  joints,  as  rapid  induration  takes  place  near  the  surface  only, 
extending  slowly  towards  the  centre,  where  it  may  remain  imperfect 
to  a  very  long  time.  This  property  it  has  in  common  with  lime  mor- 
tars and  concrete.  2d.  Cement  is  always  weakened  by  sand,  no 
matter  how  small  the  proportion  of  that  ingredient  may  be,  so  that 
if  both  materials  were  equally  cheap,  it  would  be  best  to  dispense  with 
sand  altogether  in  using  cement  as  mortar  for  building  walls,  but  not 
in  using  it  as  a  stucco  for  incrustations. 

' '  With  reference  to  the  quantity  of  sand  which  should  be  mixed 
with  cement  for  constructive  purposes,  where  strength  and  durabihty 
are  desired,  both  experience  and  experiments  clearly  show,  that  not 
more  than  two  measures  of  sand  to  one  of  cement  powder  ought  to  be 
employed  on  any  work,  and  that  when  very  important  operations  are 
involved,  five  parts  of  sand  to  four  of  cement  powder  ought  to  be  used, 
or  what  is  better,  an  equal  proportion  of  each  ingredient,  as  too  much 
sand  injures  the  cement  by  retarding  its  drying  or  setting,  and  ren- 
ders it  too  friable ;  but  with  limes  it  is  different,  for  they  will  bear  two, 
three,  or  even  more  measures  of  sand  to  one  of  lime,  without  much 
deterioration.  Upon  the  whole,  cement  sets  most  quickly  and  unites 
itself  more  powerfully  to  bricks  or  stones,  when  it  is  perfectly  pure  or 
unmixed  with  sand,  provided  the  joints  be  thin,  that  is,  not  exceeding 
half  an  inch  in  thickness. 

* '  The  construction  of  the  Thames  Tunnel  satisfactorily  established 
the  character  and  superiority  of  the  cement,  and  without  the  aid  of 
which  the  work  could  never  have  been  carried  on  to  completion,  or 
any  lengthened  period  of  durability  assured.  The  foundation  and 
lower  portions  of  the  brick-work,  having  been  laid  in  a  compost 


ANALYSIS  OF  CEMENTS. 


125 


of  equal  proportions  of  cement  and  sand ;  and  the  piers  were  built 
with  one  measure  of  sand  to  two  of  cement,  and  the  arch  work  with 
pure  cement  only. 

^'Lime  expands  by  admixture  with  water,  and  readily  attaches 
itself  to  the  particles  of  sand,  which  increase  the  bulk  and  add  much 
to  the  strength,  whereas  cement  does  not  expand,  and  is  weakened  by 
the  addition  of  sand ;  and  whilst  one  measure  of  good  calcined  lime 
powder  will  take  seven  or  eight  measures  of  gravel  to  form  a  good 
concrete,  the  cement  will  require  three  measures  of  it,  to  mix  with 
the  above  quantity  of  gravel  or  sand  to  produce  concrete  of  an  equal 
property.  Hence  cement  should  never  be  used  for  making  concrete. 
But  for  the  purpose  of  building  brickwork,  it  is  as  well  to  mix  the 
cement  with  a  moderate  quantity  of  sand,  as  the  cost  of  the  work  is 
thereby  diminished,  and  the  joints  will  become  quite  as  hard  as  the 
bricks  themselves.  Pure  cement  should  always  be  employed  for  the 
most  important  works,  or  in  particular  portions  of  them,  and  it  is  in- 
dispensable for  the  linings  of  cisterns  or  tanks,  and  the  coating  of 
casemates,  as  it  prevents  leakage,  and  renders  the  latter  perfectly 
dry,  but  it  cannot  be  depended  upon  for  such  like  purposes  if  mixed 
or  adulterated  with  sand ;  and  great  care  must  be  taken  in  the  appli- 
cation of  the  cement,  to  have  it  firmly  compressed  and  consolidated 
when  laid  on,  to  prevent  cracks  or  fissures ;  the  neglect  of  plasterers 
in  this  precaution  being  the  chief  cause  of  the  defects  in  exterior  and 
other  incrustations  where  this  cement  is  employed.  This  material 
mixed  with  a  due  proportion  of  sand,  and  applied  in  a  liquid  state, 
forms  a  most  excellent  groat." 

ON  BLACK  ROCK  OF  QUEBEC. 

'*At  the  suggestion  of  Capt.  Baddeley,  E.E.,  the  author  of  the 
treatise  now  under  notice  (Col.  Pasley,  K.E.),  by  order  of  the  British 
Government,  made  some  experiments  upon  its  character  and  qualifi- 
cation as  a  water  (or  hydraulic)  cement,  and  found  its  properties  to 
be  very  satisfactory,  although  it  was  comparatively  very  slow  in  sett- 


126 


ANALYSIS  OF  CEMENTS. 


ing,  but  in  the  end  it  acquired  a  very  stony  hardness.  For  tide  work 
he  considered  it  would  be  necessary  to  mix  it  with  boiling  water  to 
expedite  the  setting." 

ON  ARTIFICIAL  WATER   CEMENTS   AND    ON  THE  ESSENTIAL 
COMPONENTS  THEREOF 

"Natural  water  cements  being  chiefly  composed  of  carbonate  of 
lime,  silica,  alumina  and  the  oxides  of  iron,  it  appeared  that 
next  to  the  carbonate  of  lime  or  chalk,  which  is  indispensable, 
silica  and  alumina  were  the  most  important  ingredients,  for  these 
together  made  a  water  cement  without  the  iron,  whereas  the  iron 
never  succeeded  without  them,  notwithstanding  which,  it  was  of  great 
use,  since  it  caused  them  to  set  more  quickly,  and  at  the  same  time 
imparted  a  superior  degree  of  compactness  and  hardness ;  but  in  all 
cases  it  is  imperative  that  all  the  solid  ingredients  be  well  burned, 
calcined  and  reduced  to  an  impalpable  powder,  and  the  moist 
ones  must  also  be  reduced  to  the  finest  possible  state  before  being 
burned." 

In  order  to  establish  these  facts  the  author  undertook  the  following 
experiments: — 

Experiment  1st.  Carbonate  of  lime,  silica,  alumina,  with 
other  metallic  oxides,  with  the  addition  of  the  peroxide  of  iron — these 
occasionally  formed  a  good  cement,  but  the  success  of  this  mixture  is 
very  precarious.  The  addition  of  the  oxides  of  manganese  or  of  red 
lead  always  formed  good  cements  with  the  same  ingredients. 

Exp.  2d.  Carbonate  of  lime,  silica,  alumina,  with  the  carbonate 
of  magnesia.  On  mixing  measures  of  pounded  chalk,  two  measures 
of  pipe-clay,  aud  from  one  to  five  measures  of  the  carbonate  of  mag- 
nesia together — the  result  was  an  excellent  artificial  cement.  This 
cement  when  moderately  burned  was  of  a  handsome  white  color ;  but 
when  burnt  rather  more,  it  assumed  a  darkish  slate  color,  but  in 
either  case  it  was  equally  good. 


ANALYSIS  OF  CEMENTS. 


127 


"  Carbonate  of  magnesia  is  a  highly  favorable  ingredient  in  water 
cement,  producing  the  same  effect  as  protoxide  of  iron,  or  it  may  be 
said  to  be  superior  to  it,  or  to  any  other  metallic  oxide,  inasmuch  as 
the  carbonate  of  magnesia  will  sometimes  combine  with  the  carbonate 
of  lime,  alone,  into  a  good  water  cement,  which  none  of  the  metallic 
oxides  are  capable  of  effecting. 

"Exp.  3d.  Chalk  and  blue  alluvial  clay.  This  mixture  of  pounded 
chalk  and  blue  clay;  of  which  the  former  ingredient  supplies  the 
carbonate  of  lime,  and  the  latter,  the  silica,  the  alumina,  and 
the  protoxide  of  iron,  was  successful,  and  is  here  placed  among  the 
quadruple  compounds.  Having  tried  various  proportions  of  the  above 
ingredients,  the  following,  which  most  resembles  the  Sheppy  cement  in 
its  qualities,  was  adopted,  viz.,  five  measures  of  chalk  to  two  measures 
of  moist  clay.  Three  measures  of  chalk  to  one  of  clay  will  also  make 
a  good  water  cement,  but  not  equal  to  the  former  proportions.  An 
excess  of  chalk  such  as  three  and  a  half,  four  or  five  to  one,  spoils 
the  mixture  as  a  water  cement,"  but  converts  it  into  a  *^  water 
lime."  A  smaller  portion  of  chalk,  on  the  contrary,  such  as  two  to 
one,  makes  a  very  good  water  cement,  and  even  one  and  a  half  meas- 
m-e  of  chalk  to  one  of  clay,  makes  a  good  cement,  but  one  that  sets 
slowly  and  with  moderate  heat,  for  as  the  quantity  of  chalk  is  diminish- 
ed, so  is  the  heat  of  setting,  whilst  the  period  required  for  that  pro- 
cess is  prolonged." 

CONCLUSIONS  DRAWN  FROM  OTHER  EXPERIMENTS. 

That  alluvial  clay  is  brown  at  the  surface,  where  it  is  exposed  to 
the  air,  and  that  this  brown  part  will  not  form  a  water  cement.  That 
blue  clay  fresh  from  a  river,  which  forms  an  excellent  ingredient  for 
an  artificial  water  cement,  loses  this  property  when  it  becomes  stale 
by  exposure  to  the  air,  which  also  deprives  it  of  its  color. 

"That  repeated  washings  spoil  alluvial  clay. 

"That  chalk  and  fine  brown  pit  clay  make  a  good  cement. 

**That  tile-dust,  slate-dust,  and  Euller's  earth  failed;  and  that  as 


128 


ANALYSIS  OF  CEMENTS. 


none  of  these  are  plastic,  which  property  seems  necessary  in  clay  as  an 
ingredient  for  a  water  cement — 

*'  That  Fuller's  earth  is  much  improved,  and  rendered  plastic  by  re- 
peated washing. 

"That  hard  stone  if  used  as  an  ingredient  for  a  water  cement, 
must  be  burned  twice,  first  in  its  natural  state,  and  afterwards  mixed 
with  clay. 

* '  That  lime  and  clay  burned  separately  failed  in  making  an  artifi- 
cial cement,  on  immediate  immersion,  but  may  be  useful  for  many 
hydraulic  purposes,  though  inferior  both  to  the  natural  and  artificial 
cements." 

Then  follows  a  series  of  experiments  to  ascertain  by  what  additional 
substances,  the  best  natural  cements  may  be  spoiled,  from  which  the 
following  conclusions  are  deduced,  viz. : — 

"That  salt  is  very  prejudicial  to  brick  earths. 

"That  the  carbonate  of  magnesia  was  the  only  substance  which 
did  not  spoil  the  Sheppy  cement. 

"  That  the  latter  ingredient  is  itself  a  water  cement,  but  a  slow 
setting  one. 

"That  all  the  author's  experimental  cement  which  had  succeeded 
in  setting  under  water,  also  resisted  the  severest  frosts,  quite  as  well 
as  the  natural  cements,  after  rigorous  tests  to  which  they  were  ex- 
posed in  the  winter  of  1829—  30. 

"That  the  best  cements,  though  perfectly  'frost-proof,'  may  be 
injured  by  frost,  if  applied  as  stucco  in  an  injudicious  manner.'* 


129 


VARIOUS  RECIPES  FOR  CEMENTS,  MORTARS,  ETC. 

FOR  BUILDING  AND  INCRUSTATIONS. 

A  Strong  mastic  cement  for  coating  walls,  &c.,  is  prepared  as  fol- 
lows :  20  parts  of  clean  river  sand,  2  parts  of  litharge  (red  lead),  and 
1  part  of  quick-lime,  mixed  into  a  thin  putty  with  linseed  oil. 

Dalits  cement  for  covering  fronts  of  buildings  consists  of  linseed 
oil,  rendered  dry  by  boiling  with  litharge,  and  mixed  with  porcelain 
clay  in  fine  powder,  or  pipe-clay  well  ground,  and  colored  with  ground 
bricks  or  pottery.  A  little  oil  of  turpentine  added,  to  thin  this  ce- 
ment, aids  it  in  its  cohesion  to  brick,  stone,  &c., 

Hamlin's  cement  is  composed  of  fifty  measures  of  siliceous  sand 
fifty  of  lime  marl,  and  nine  of  litharge,  ground  up  with  linseed  oil. 
This  material  has  been  in  much  use  and  repute  in  England  and  else- 
where. 

Leardefs  (or,  as  it  is  commonly  called,  Adam's")  oil  cement  or 
stucco,  is  prepared  in  the  following  manner  :  for  the  first  coat,  take 
21  pounds  of  fine  whiting,  or  oyster  shells,  or  any  other  sea  shells  cal- 
cined, or  plaster  of  Paris,  or  any  other  suitable  calcareous  material, 
calcined  and  pounded;  add  white  or  red  lead  at  pleasure,  deducting 
from  the  other  absorbent  materials  in  proportion  to  the  weight  of 
the  red  or  white  lead  added,  to  which  put  four  quarts  (beer  measure)  of 
oil,  and  mix  them  together  in  a  grinding  mill,  or  in  any  levigating 
machine,  and  afterwards  mix  and  beat  up  the  same,  well,  with  28 
quarts  of  sand  or  gravel,  or  of  both,  mixed  and  sifted,  or  of 
pounded  stone  or  marble,  or  any  solid  and  suitable  material. 

For  the  second  coat,  16  ^  pounds  of  superfine  whiting,  or  oyster 

shells,  &c.,  as  for  the  first  coat,  16  ^  pounds  of  white  or  red  lead, 

6  \  quarts  of  oil,  and  mix  them  together  as  before  described  ;  add  30 

quarts  of  fine  sand,  gravel,  &c.,  as  before  noted,  and  mix  and  beat  them 

up  well  together ;  varying  the  proportion  of  sand  or  gravel,  &c.,  as  the 
6* 


130 


VARIOUS  RECIPES. 


nature  of  the  work  may  require.  In  preparing  this  composition  the  best 
linseed  or  hempseed  or  other  proper  oils,  suited  for  the  purpose,  must  be 
employed,  either  boiled  or  raw,  with  such  drying  ingredients  as  the 
nature  of  the  work,  climate,  season,  or  other  circumstances  may  de- 
mand ;  and  in  some  cases,  bees-wax  may  be  substituted  for  oil.  All 
the  absorbent  and  solid  materials  must  be  kiln-dried. 

Tliis  cement  is  applied  in  the  usual  manner,  but  previous  to  laying 
it  on,  it  may  be  proper  to  wet  the  surface  on  which  it  is  to  be  laid, 
with  the  same  sort  of  oil  and  other  ingredients  which  have  passed 
through  the  levigating  machine,  reduced  to  a  more  liquid  state  and 
applied  with  a  brush,  in  order  to  make  the  composition  adhere  the 
better. 

This  composition  admits  of  being  modeled  or  cast  in  molds  in  the 
same  manner  as  statuaries,  plasterers,  &c.,  model  or  cast  their  stucco 
work.  It  also  admits  being  painted  upon,  and  adorned  with  land- 
scapes, figures,  &c. 

A  good  cement  is  prepared  from  equal  quantities  of  powdered  glass, 
sea-salt,  and  iron  filings,  mixed  with  burnt  loam,  which  becomes  very 
hard  and  durable. 

Beavari's  mortar,  or  building  cement,  is  composed  of  marble,  flint, 
chalk,  lime  and  water,  and  when  dry  is  capable  of  a  high  polish.  Its 
proportions  are,  equal  parts  of  marble,  flint  and  chalk  ;  pulverized, 
mixed  together,  and  passed  through  a  very  fine  sieve  ;  add  to  this  one 
part  of  lime  which  has  been  slaked  three  months,  and  sufiicicnt  water 
to  make  the  whole  into  a  thin  paste ;  and  in  this  state  it  is  to  be  ap- 
plied over  a  coai'se  ground  (or  previous  coat),  as  thin  as  possible,  and 
rendered  smooth  on  the  surface ;  and  when  dry  may  be  polished  by 
Venetian  talc.  If  buildings  are  to  be  covered  with  it,  a  preparatory 
rough  ground  should  be  attached,  formed  of  river  sand  and  lime. 

Venetian  cement,  used  in  the  Italian  provinces  for  covering  floors, 
terraces  and  roofs  of  houses,  the  secret  of  which  is  not  precisely  known, 
is  believed  to  be  compounded  of  plaster  of  Paris,  sulphur,  resin,  pitch, 
and  spirit  of  turpentine,  or  wax,  mixed  and  applied  hot. 


VARIOUS  RECIPES. 


131 


Smeatori's  cement,  used  in  the  construction  of  the  far-famed  Eddy- 
stone  lighthouse,  in  the  British  Channel,  was  composed  of  equal  quan- 
titias  of  Puzzolana  and  Aberthaw  lime ;  this  mixture  was  calculated 
as  best  able  to  withstand  the  utmost  violence  of  the  wa\es  which  are 
continually  beating,  and  oftentimes  with  violent  shocks,  the  substruc- 
ture of  the  building ;  and  truly  has  that  conjecture  been  verified  by 
the  test  and  experience  of  many  years  and  sundry  storms. 

Two  bushels  of  slaked  Aberthaw  lime,  one  bushel  of  Puzzolana,  and 
three  of  clean,  sharp  sand,  will  form  a  good  water-cement. 

Dutch  trass,  terras,  or  tarras,  or  as  sometimes  called  in  Holland, 
wakke,  is  a  basaltic  mineral,  found  in  the  Low  countries,  and  abun- 
dantly used  in  the  construction  of  mounds,  weirs,  and  other  aquatic 
works.  This  celebrated  mortar  is  made  by  covering  a  previously  pre- 
pared mass  of  quick-lime  of  about  a  foot  in  thickness  (and  sprinkled 
with  water),  with  an  equal  quantity  of  powdered  terras,  and  then  left 
for  two  or  three  days,  after  which,  the  quantity  required  for  imme- 
diate use  is  separated  from  the  bulk,  and  beaten  up  to  a  pro]:>er 
consistency. 

One  measure  of  quick-lime,  and  two  of  slaked-lime,  in  powder,  and 
one  of  terras,  well  mixed  and  beaten  together  to  the  consistence  of 
paste,  with  as  little  water  as  possible,  forms  the  terras  mortar  in 
general  use ;  and  a  cheaper  kind  is  made  by  mixing  two  parts  of 
slaked  lime,  one  of  terras,  and  three  of  coarse  sand  together.  These 
cements  indurate  very  quickly  under  water  and  remain  very  firm. 

The  trifa  stone,  which,  when  ground,  forms  trass  or  terras,  con- 
tains 57.0  silica,  16.0  clay,  2.6  lime,  1.0  magnesia,  7.0  potash,  1.0 
soda,  5.0  oxide  of  iron  and  titanum,  and  9.6  water;  it  is  found  abun- 
dantly in  the  north  of  Ireland,  among  the  schistoze  formations  on  the 
banks  of  the  Rhine,  and  at  Manheim  in  Bavaria. 

The  fatter  the  lime,  the  less  of  it  must  be  added  to  the  trass  to 
make  hydraulic  cement ;  the  mixture  should  be  made  extempora- 
neously, and  kept  dry  till  used.  When  it  hardens  too  soon  (as  in  twelve 
hours)  it  is  apt  to  crack,  but  if  it  takes  six  or  eight  days  to  indurate,  it 


132 


VARIOUS  RECIPES. 


is  better ;  through  the  medium  of  water,  silicates  of  lime,  alumina, 
clay,  and  the  oxide  of  iron  are  formed,  which  soon  become  hard  . 

"  Beside  the  two  volcanic  products  just  described,  all  lime-stones 
which  contain  from  20  to  30  per  cent  of  silica  are  fitted  for  hydraulic 
cements ;  but  much  depends  upon  the  proportion  of  silica  present,  and 
the  physical  structure  of  all  the  constituents. 

Meagre  or  poor  lime-stones  are  best  suited  for  hydraulic  mortar, 
such  as  contain  from  8  to  25  per  cent,  of  foreign  matter,  such  as  sili- 
ca, alumina,  magnesia,  &c. ;  these,  though  calcined,  do  not  slake  when 
wetted ;  but  when  pulverized,  will  absorb  water  without  heat  or  swell- 
ing, and  form  a  paste  which  will  harden  under  water  in  a  few  days, 
but  will  never  become  greatly  indurated  by  simple  exposure  to  the  air. 

All  sorts  of  lime  can  be  made  hydraulic  by  mixing  slaked  lime  with 
solutions  of  common  alum,  or  sulphate  of  alumina;  but  the  best 
method  consists  in  employing  a  solution  of  silicate  of  potash  (called 
liquor  of  flints,  or  soluble  glass),  to  mix  with  the  lime,  or  lime  and 
clay.  Also  by  adding  silica  and  alumina,  or  merely  the  former  to 
good  fat  lime,  a  water-cement  may  be  artificially  formed ;  and  like- 
wise by  adding  to  lime  or  other  natural  productions  which  contain  sili- 
cates— puzzolanas,  trass,  pumice-stone,  basalt,  trifa,  slate  clay,  &c. 

Ground  felspar,  or  clay,  if  previously  calcined  with  the  lime,  will 
form  an  hydraulic  cement. 

Beton  (French),  used  for  constructing  marine  works,  consists  of  12 
parts  of  puzzolana,  or  Dutch  trass,  6  parts  of  sand,  9  parts  of  un- 
slaked lime,  13  parts  of  stone  fragments,  about  the  size  of  an  egg,  3 
parts-of  tile  dust,  cinders  or  scales  from  a  forge  ;  the  whole  well  worked 
and  beaten  together. 

A  composition  for  incrustations  may  be  formed  of  lime-stone,  road- 
drift,  sand,  or  similar  substances,  with  the  powder  of  burnt-bones ; 
these  ingredients  are  to  be  powdered,  mixed  together  and  heated  in 
an  oven,  and  while  hot  to  be  mixed  with  one-fourth  part  of  tar^ 
pitch,  or  resin,  and  applied  warm ;  this  will  be  found  a  good  covering 
for  ro(;fs,  floors,  terraces,  &c. 


VARIOUS  RECIPES. 


133 


Plaster  of  Paris,  with  an  admixture  of  one  tenth  part  of  rust  of 
iron,  or  iron  scales  or  filings,  makes  a  water-cement  which  sets  very 
quickly  and  is  of  great  hardiess,  and  if  boiled  potatoes  be  incorpora- 
ted mth  mortar  of  lime  and  sand  or  with  mortar  containing  burnt 
clay,  these  compositions  will  be  much  improved. 

A  composition  said  to  equal  Roman  cement  is  made  by  dissolving 
three  pounds  and  a  half  of  sulphate  of  iron,  and  mixing  them  with  a 
bushel  of  lime,  and  half  a  bushel  of  fine  gravel  sand,  previously  made 
into  mortar. 

Parker's  Roman  cement,  for  incrustations  and  general  building  pur- 
poses, is  a  composition  forming  an  artificial  stone,  and  being  imper- 
vious to  water  is  very  valuable.  This  material,  when  incorporated 
with  an  equal  quantity  of  clean  sharp  grit  sand,  well  beaten  up  with 
a  suflficiency  of  water,  and  applied  quickly,  forms  a  handsome  and 
durable  covering  for  fronts  of  houses ;  and  one  bushel  of  the  cement, 
with  the  addition  of  sand,  &c.,  is  considered  sufficient  to  cover  about 
four  square  yards  of  surface. 

Ancient  MaUha.  The  Roman  and  Greek  architects  gave  the  term 
of  maltha  to  a  calcareous  cement  used  as  stucco,  and  this  and  the 
term  mastic  are  given  to  various  compositions. 

The  mixture  of  milk  with  lime  and  sand  is  said  to  have  constituted 
the  maltha  of  the  Greeks ;  and  we  learn  from  Pliny,  that  Roman 
maltha  was  made  by  mixing  fresh-burnt  lime,  slaked  with  wine,  and 
beaten  in  a  mortar,  with  hog's  lard  and  figs.  This  composition  is  re- 
ported to  possess  great  tenacity,  and  acquires  the  hardness  of  granite. 

Another  kind  was  made  of  powder  of  slaked  lime,  mixed  with  bul- 
lock's blood  and  powdered  scales  of  the  gray  oxide  of  iron. 

Previous  to  applying  the  maltha,  the  surface  of  the  wall  or  ceiling 
was  smeared  over  with  oil  to  make  the  composition  adhere. 

Dr.  Shaw  gives  the  following  particulars  of  a  species  of  maltha 
which  the  inhabitants  of  Tunis  and  of  other  places  in  Africa  use  for 
incrustations,  &c.  One  measure  of  sand,  two  of  wood-ashes,  and 
three  of  sifted  lime  powder  are  mixed  together  with  a  very  little  water, 


134 


VARIOUS  RECIPES. 


and  after  this  mixture  has  been  well  beaten,  a  little  oil  is  added ;  the 
beating  is  then  resumed,  and  continued  for  three  or  four  days  occas- 
sionally,  during  which,  the  proper  degree  of  softening  is  preserved  by 
alternately  adding  small  quantities  of  water  and  oil.  In  a  short  time 
after  its  application  it  acquires  the  hardness  of  stone. 

A  cement  of  a  gray  color,  found  upon  examination  to  be  composed 
of  an  admixture  of  unslaked  lime,  pulverized  charcoal,  and  powdered 
sandstone,  was  discovered  in  the  construction  of  a  mausoleum  of  some 
of  the  Tartar  princes.  The  spaces  between  the  bricks  were  about  an 
inch  broad,  and  the  cement  had  acquired  such  a  solid  consistence 
that  it  was  found  easier  to  break  the  well-burnt  bricks  than  to  separ- 
ate or  detach  the  cement. 

A  composition  for  mouldings,  &c.,  is  prepared  from  two  pounds  of 
powdered  whiting,  one  pound  of  glue,  mixed  with  half  a  pint  of  oil, 
and  thoroughly  incorporated  in  a  metal  vessel  by  means  of  heat,  and 
then  well  beaten  on  a  stone  with  whiting,  till  it  has  acquired  the 
necessary  consistence  and  toughness.  It  is  kept  under  moist  cloths 
until  used.  The  ornaments  or  mouldings  when  cast  and  dry  are 
affixed  to  the  surfaces  by  means  of  glue  or  white  lead. 

A  delicate  cement  for  small  work,  is  made  by  heating  a  pint  of 
milk  to  the  boiling  point,  and  adding  vinegar  till  the  curd  separates, 
then  straining  off  the  whey,  which  must  be  beaten  up  with  the  whites 
of  four  or  five  eggs,  gradually  adding  the  whey  again.  When  the 
whole  is  well  mixed,  sifted  quicklime  is  to  be  stirred  in  until  the 
consistence  becomes  like  a  thick  paste.  The  prepared  liquid 
alone  may  be  kept,  if  closely  corked  up,  but  the  lime  must  only 
be  added  when  required  for  use.  This  composition  resists  the  ac- 
tion of  fire  and  water,  and  is  chiefly  used  to  replace  deficiencies 
in  small  works,  and  to  fasten  fragments  together,  which  it  unites 
firmly. 

A  cement  for  stopping  holes  and  cracks  in  marble  or  stone,  and  for 
veneering  marble,  for  inlaying  and  mosaic  work,  is  made  of  a  pound 
of  bees-wax,  sliced,  melted  with  a  quarter  of  a  pound  of  resin,  powder- 


VARIOUS  RECIPES. 


135 


ed,  to  which  add  an  ounce,  each,  of  chalk  and  brick-dust,  both  finely 
powdered,  the  whole  to  be  well  boiled  and  mixed  up  together.  This 
cement  must  be  used  hot,  and  the  substance  to  which  it  is  applied 
must  be  previously  heated. 

The  cold  cement  for  the  like  purpose  or  for  mending  earthenware, 
&c.,  and  which  is  reckoned  a  great  secret  among  workmen,  is  made 
by  grating  a  pound  of  old  Cheshire  cheese,  with  a  bread  grater,  into 
a  quart  of  milk,  in  which  it  must  remain  fourteen  hours,  stirring  it 
frequently,  a  pound  of  unslaked  lime  in  powder  must  then  be  added, 
and  the  whole  well-beaten  up,  and  finally  add  the  whites  of  twenty  or 
thirty  eggs,  beaten  up  with  any  coloring  matter  desired,  and  let  the 
whole  be  well  mixed  and  beaten  up  together. 

The  hot  cement  is  made  of  resin,  beeswax,  brick-dust,  and 
chalk  boiled  together.  The  bricks  or  other  substance  to  be  united, 
must  be  heated,  and  their  surfaces  rubbed  together  with  the  cement 
between  them,  as  carpenters  make  a  glued  joint  in  boards. 

FrosVs  water  cement  is  composed  of  carbonate  of  lime,  calcined  at 
a  heat  not  exceeding  that  at  which  cast-iron  softens,  and  cooled 
without  access  of  atmospheric  air  or  moisture,  acquires  the  property 
of  quickly  hardening  under  water,  and  mixed  with  silicious  sand  and 
water,  forms  an  artificial  Puzzolana,  or  Roman  cement. 

Dohhs'  ce77ient  for  water-proof  purposes,  is  composed  of  carbonate 
of  lime  (burnt  as  for  common  plaster)  mixed  up  with  water,  clay 
loam,  shale,  road  drift,  metallic  oxides,  ores,  sand,  or  any  other 
earthy  substance  which  will  bear  a  sufficient  heat  for  calcination.  The 
whole  of  these  ingredients  are  then  to  be  reduced  to  a  fine  powder, 
mixed  with  a  water,  and  left  in  proper  vessels  till  it  has  subsided. 
The  water  is  then  to  be  poured  off  and  the  plastic  materials  formed 
into  square  pieces  and  dried,  after  which  they  are  to  be  subjected  to 
the  heat  of  a  lime-kiln  or  stove,  and  lastly  mixed  with  the  lime  and 
water  for  the  intended  purposes. 

A  good  incrustation  cement  is  made  with  one  hundred  parts  of 
quick  lime,  five  of  white  or  colored  clay,  and  two  of  yellow  ochre;  it 


136 


VARIOUS  RECIPES. 


forms  a  cement  which  is  tenacious,  and  remains  unchangeable  when 
exposed  to  the  weather.  The  process  of  its  manufacture  is  thus  :  The 
lime  must  be  first  slaked  with  a  small  quantity  of  water,  more  of 
which  must  afterwards  be  added  till  of  the  consistence  of  cream. 
White  clay  is  at  the  same  time  mixed  to  a  similar  condition,  and 
after  remaining  some  time  apart,  the  two  solutions  are  carefully 
mixed  together.  During  the  continuance  of  this  mixture  in  a  tub 
for  twenty-four  hours,  it  should  be  frequently  stirred,  and  a  portion 
of  yellow  ochre  added  to  give  it  an  agreeable  color.  Walls  covered 
with  this  cement  have  remained  exposed  to  the  weather  for  years, 
without  injury. 

M.  Berthier  is  of  opinion  that  with  one  part  of  common  clay,  and 
two  parts  and  a  half  of  chalk,  a  very  good  hydraulic  lime  may  be 
made  which  will  set  as  quickly  as  Parker's  cement.  He  concludes 
that  a  lime-stone,  which  contains  six  per  cent  of  clay,  affords  a  mor- 
tar precisely  "hydraulic." 

Lime  possessing  from  fifteen  to  twenty  per  cent  of  clay,  is  very 
hydraulic,  and  when  from  twenty-fiA^e  to  thirty,  it  sets  almost  instant- 
ly, and  may  therefore  be  held  to  be  a  perfect  Roman  cement.  But 
an  argillaceous  lime-stone,  which,  when  slaked,  increases  its  bulk  from 
one  to  three  parts  in  ten,  and  which  when  in  the  form  of  slaked  paste, 
will  take  from  one  hundred  to  one  hundred  and  sixty  measures 
of  sand,  will  afford  at  a  moderate  cost,  a  cement  well  fitted  to 
resist  atmospheric  changes,  and  constant  exposure  to  a  running 
stream. 

A  little  manganese  added  to  mortar  imparts  the  property  of  hard- 
ening under  water,  and  lime-stone  is  frequently  found  combined 
with  this  mineral,  which  gives  it  a  brown  color  when  burnt. 

The  essential  constituents  of  all  good  hydraulic  mortars  are  caustic 
lime  and  silica,  the  hardening  of  which  under  water  merely  consists 
in  their  chemical  combinations,  through  the  medium  of  water,  pro- 
ducing a  hydrated  silicate  of  lime.  Quartoze  sand,  however  finely 
powdered  wiU  form  no  water  mortar  with  lime,  but  if  the  powder  be 


VARIOUS  RECIPES. 


137 


ignited  by  the  lime,  it  will  be  rendered  fit  for  hydraulic  works. 

Bituminous  Ime-stone  dried,  ground,  sifted,  and  mixed,  with  about 
its  own  weight  of  melted  pitch  or  coal  tar,  may,  when  in  a  semi-fluid 
state  be  moulded  into  blocks  or  slabs,  and  be  applied  for  floors  of  ter- 
races, balconies,  roofs  of  houses,  or  linings  of  tanks  and  reservoirs, 
conduits,  drains,  &c.,  but  when  laid,  the  joints  must  be  run  together 
with  hot  irons.  The  terrace  floor  must  be  previously  covered  with  a 
layer  of  plaster-of-paris  or  common  mortar,  laid  to  the  required  slope 
or  level,  about  an  inch  to  the  yard.  It  weighs  about  144:  lbs.  to  the 
cubic  foot,  consequently  one  foot  square,  and  one  inch  thick  will 
weigh  12  lbs. 

RECIPES 

FOR  MANUrACTURING  AND  DOMESTIC  PURPOSES. 

Iron-rust  cement :  100  parts  of  iron  borings  or  filings,  powdered 
and  sifted,  and  mixed  with  one  of  sal-ammoniac,  and  when  applied 
must  be  mixed  and  well  incorporated  together,  with  as  much  water  as 
will  give  it  a  pasty  consistency  ;  or  4  parts  of  fine  borings,  2  parts  of 
potter's  clay  and  1  of  powdered  potsherds,  mixed  as  above.  This  ce- 
ment is  good  for  making  joints  &c.,  to  ironwork,  and  if  allowed  to 
concrete  slowly  becomes  very  hard. 

Plumber's  cement :  1  part  of  black  resin  and  2  parts  of  pulverized 
and  sifted  brick-dust,  well  incorporated  together  with  a  melting  heat. 

Coppersmith's  and  engineer's  cement:  Boiled  linseed  oil  and  red 
lead,  mixed  into  a  putty  ;  or  bullock's  blood  and  quick-lime. 

Diamond  cement,  for  mending  china,  glass,  porcelain,  &c.,  is  com- 
posed of  isinglass,  soaked  in  water  till  soft,  then  dissolved  in  proof- 
spirit,  to  which  are  added  a  little  gum-resin,  ammoniac,  or  galbanum, 
and  resin  mastic,  each  being  previously  dissolved  in  a  minimum  of 
alcohol ;  and  when  applied  must  be  gently  heated,  in  order  to  liquify 
it^  and  when  not  required  should  be  kept  in  a  well-corked  bottle. 

Other  cements  for  the  like  purpose  :  Gum  shellac  dissolved  in  alco- 
hol^ or  in  a  solution  of  borax,  makes  a  good  cement. 

White  of  eggs  (albumen),  mixed  with  finely  powdered  quick-lime^ 


138 


VARIOUS  RECIPES. 


forms  a  good  cement  for  joining  substances  which  are  not  exposed  to 
much  moisture. 

Skim  milk  cheese^  cut  in  slices,  and  boiled  to  a  gluey  consistence  in 
a  quantity  of  water,  and  then  incorporated  with  quick-lime  on  a  slab 
with  a  muller ;  is  applied  to  mend  broken  stone-ware,  and  when  cold 
unites  very  firmly. 

Melted  brimstone  (sulphur)  used  either  alone  or  mixed  with  resm 
and  brick-dust,  makes  a  tolerably  good  and  cheap  cement. 

Jeweller  s  cement  is  composed  of  resin,  beeswax,  and  finely  sifted 
brick  dust,  and  is  in  use  amongst  goldsmiths,  jewellers  and  engravers, 
to  fix  metals,  stones,  &c.,  to  be  engraved  or  operated  upon,  firm  to 
the  block. 

Carpenter^s  cement :  Take  equal  quantities  of  pounded  resin  and 
beeswax,  mixing  them  together  over  a  slow  fire,  during  which  pro- 
cess add  as  much  powdered  chalk,  yellow  ochre,  or  burnt  ochre,  as  will 
produce  the  required  color,  and  when  well  incorporated  together,  ap- 
ply hot ;  or — 

Take  fine  saw-dust  of  the  wood  you  wish  to  imitate,  and  macerate 
it  in  water  for  two  or  three  days ;  then  pour  ofi*  a  part  of  the  water, 
and  boil  the  residue  until  it  becomes  smooth  and  pulpy.  Keep  it  well 
covered  up  for  use,  and  when  required,  mix  as  much  glue  with  it  as 
necessary.  These  cements  are  very  useful  for  stopping  up  flaws  in 
wainscotting,  and  for  other  purposes. 

A  cement  for  fixing  mouldings,  fillets,  ornaments,  &c.,  can  be  made 
by  dissolving  isinglass,  and  adding  glue  to  it  which  has  been  soaked 
twenty-four  hours,  and  straining  the  compound  through  a  fine  sieve,  or 
coarse  cloth. 

A  cement  for  closing  and  repairing  pipes  of  subterraneous  aqueducts, 
is  composed  of  pulverized  tobacco-pipe  clay,  mixed  with  a  large  quan- 
tity of  pulverized  flocks,  tempered  with  linseed  oil,  and  well  beaten 
into  a  stiff"  paste. 

A  cement  for  fastening  the  receiver  of  an  air-pump  to  a  metallic 
plate,  is  made  with  equal  parts  of  beeswax  and  turpentine  (for  winter 


VARIOUS  RECIPES. 


139 


use),  or  three  parts  of  beeswax  to  two  of  turpentine,  for  summer  use. 

ChemisVs  cement,  for  repairing  chemical  glasses  or  vessels,  and 
which  will  bear  the  fire,  is  made  with  equal  quantities  of  wheat  flour, 
fine  powdered  Venice  glass,  pulverized  chalk,  with  half  the  quantity 
of  fine  brick-dust,  a  little  scraped  lint,  and  the  whites  of  eggs,  well 
and  properly  incorporated  together.  This  mixture  is  to  be  spread 
thinly  but  evenly  on  linen  cloth,  and  then  applied  to  the  fractured 
parts  of  the  glass,  and  the  whole  should  be  well  dried  before  subjected 
to  fire ;  or  old  varnish  is  said  to  answer  the  same  purpose. 

Electrical  cement,  for  electrical  purposes,  is  compounded  of  two 
pounds  of  resin,  two  of  beeswax,  and  one  of  powdered  red  ocher,  the 
whole  mixed  and  melted  together,  and  kept  close  for  use;  or  five 
pounds  of  resin,  one  of  beeswax,  one  of  red  ocher,  and  two  table-spoon- 
fuls of  plaster  of  Paris,  well  melted  together. 

A  bituminous  cement  :  Sixteen  parts  of  whiting,  sifted  and 
thoroughly  dried  by  a  white  heat,  the  like  quantity  of  black  resin,  and 
one  part  of  beeswax,  to  be  added  to  the  former  ingredients  while  cool, 
stirring  the  whole  together  while  cooling, 

A  cement  for  uniting  voltaic  plates  and  wooden  troughs,  is  com- 
posed of  six  pounds  of  resin,  one  of  red  ochre,  half  a  pound  of  plaster 
of  Paris,  and  a  quarter  of  a  pound  of  linseed  oil.  The  ochre  and 
plaster  of  Paris  must  be  previously  calcined,  and  added  to  the  other 
ingredients  when  in  their  molten  state,  and  the  thinner  the  stratum 
of  cement  applied,  the  stronger  will  be  the  joint. 

Statuary^s  cement,  for  joining  alabaster,  marble,  porphyry  and 
other  stones,  is  prepared  as  follows :  Melt  two  pounds  of  bee's  wax 
and  one  pound  of  resin  together ;  add  one  pound  and  a  half  of  the 
same  material,  pulverized,  as  the  body  to  be  cemented  is  composed 
of,  and  stir  them  well  together ;  let  the  mass  be  warmed  together,  and 
when  applied,  the  body  or  matter  to  be  cemented,  should  be  heated. 
The  required  color  can  be  obtained  by  varying  the  proportions  of  the 
powdered  matter,  and  the  mass  of  bee's  wax  and  resin. 

Steam  cement.     This  is  not  only  useful  for  cementing  different 


140 


VAKIOUS  RECIPES. 


parts  of  hydraulic  and  steam  engines,  but  also  for  repairing  broken 
stone,  &c.  It  consists  of  boiled  linseed  oil,  litharge,  and  red  and 
white  lead,  mixed  to  a  proper  consistence,  aud  applied  on  each  side  of 
a  piece  of  flannel  previously  cut  to  the  shape  of  the  joint  of  iron  or 
other  substance,  and  put  between  the  pieces  before  being  screwed  to- 
gether, or  hammered,  or  brought  home"  as  the  workmen  term  it. 
By  this  means  a  close  and  durable  joint  is  made.  Care  must  be  taken 
not  to  leave  the  mixture  too  thin  with  oil,  and  as  the  white  lead  does 
not  dry  so  quickly  as  the  red,  more  of  the  latter  ought  to  be  used. 
When  the  fittings  will  not  admit  the  substance  of  flannel,  linen,  paper 
or  thin  pasteboard,  may  be  substituted. 

The  following  cement  answers  well  for  joining  broken  stones  of  the 
largest  kind,  and  stone  joints  set  with  this,  never  leak  or  want  future 
repairs ;  and  if  the  stone  be  thick,  not  more  than  an  inch  next  the 
water  need  be  filled  with  the  cement,  the  rest  may  be  done  with  com- 
mon mortar :  Two  ounces  of  sal-ammoniae,  one  ounce  of  flower  of 
sulphur,  and  sixteen  ounces  of  cast-iron  filings  or  borings;  mix  them 
in  a  * '  mortar, "  and  keep  the  powder  dry.  When  this  cement  is 
wanted,  take  one  part  of  the  above,  to  twenty  parts  of  clean  iron 
filings  or  borings,  and  mix  them  intimately,  and  beat  to  a  powder  in 
a  mortar.  When  mixed  to  a  proper  consistence  with  water,  apply  it 
with  a  wooden  or  iron  spatula. 

This  is  the  cement  used  in  the  filling-up  and  clasping  the  joinings 
of  Southwark  cast-iron  bridge,  built  over  the  river  Thames  (Lon- 
don) by  the  late  Sir  John  Rennie.  The  chemical  action  of  all  these 
ingredients  on  one  another  causes  the  whole  to  unite  in  a  hard  homo- 
genous mass. 

Flooring  cement  may  be  made  of  two-tlyrds  of  lime,  and  one  of 
coal-ashes,  well  sifted,  added  to  a  small  quantity  of  clay;  then  mix  the 
whole  together  with  water,  temper  well,  and  make  into  a  heap,  let  it 
remain  for  a  week  or  ten  days,  then  temper  again,  heating  it  until  it 
acquires  a  proper  tenacity  and  consistency. 

The  surface  upon  which  it  is  to  be  applied  being  made  perfectly 


VAKIOUS  RECIPES. 


Ul 


level  or  smooth,  lay  the  composition  on,  about  two  and  a  half  or  three 
inches  thick,  working  it  smooth  with  a  trowel.  If  a  better  floor  be 
required  for  superior  apartments,  cover  this  first  layer  with  another, 
made  of  the  lime  of  rag-stones,  well  tempered  with  whites  of  eggs, 
laid  on  about  half  an  inch  thick,  before  the  first  covering  or  layer  be- 
comes too  dry. 

When  the  whole  is  thoroughly  dried,  and  rubbed  with  a  little  oil, 
it  will  be  as  smooth  as  polished  marble.  This  cement  is  also  adapted 
for  roofs  and  walls. 

RECIPES. 

The  following  recipes  are  from  Colonel  Fanshawe's  memoranda, 
and  remarks  on  hydraulic  mortars,  descriptive  of  different  sorts  used 
at  Water  Point,  Gibraltar,  in  the  year  1790 — 1  : — 

1st.  Coal-ash  mortar.  This  consisted  of  lime  two  and  a  half 
measures,  sand  two  and  a  half,  coal-ashes  two  and  half,  Puzzolana 
one  and  a  half,  and  smith's  cinders  one  and  a  half,  the  proportion  of 
lime  to  the  other  ingredient,  thus  being  one  to  three  and  a  half. 

2d.  Dutch  terras  mortar.  This  was  formed  of  equal  parts  of 
lime  and  trass,  by  measure. 

3d.  Puzzolana  mortar,  which  consisted  of  the  like  propor- 
tions of  lime  and  Puzzolana. 

4th.  Puzzolana  mortar  for  lining  cisterns  and  coating 
the  roofs  of  casemates.  This  consisted  of  slaked  lime  sixteen 
measures,  Puzzolana  eight,  sand  five  and  a  quarter,  beaten  glass  four, 
and  smith's  cinders  four,  the  proportion  of  lime  to  the  other  ingredi- 
ents being  as  one  to  one  and  two-thirds  nearly. 

notes  on  puzzolana. 

Col.  Pasley  draws  the  following  inferences  from  various  experiments 
upon  the  effects  of  Puzzolana,  when  mixed  with  other  cementitious 
matters. 

1st.  That  Puzzolana  is  very  injurious  to  cement. 


142 


PUZZOLANA, 


2d.  It  imparts  to  chalk-lime  the  important  property  of  setting  un- 
der water  and  to  increase  its  adhesiveness  to  a  moderate  extent  when 
mixed  in  the  proportion  of  two  measures  of  Puzzolana  powder  to  one 
of  lime  paste ;  but  it  increases  the  resistance  of  this  lime  in  a  most 
extraordinary  degree,  nearly  six-fold,  rendering  it  in  seventeen  days 
nearly  double  of  the  resistance  of  the  best  concretes  and  mortars  made 
of  the  same  lime,  mixed  with  gravel  and  sand  alone,  though  eight  to 
twelve  months  old  and  upwards. 

3rd.  That  the  effect  of  Puzzolana  on  common  chalk  lime,  mixed 
with  sand,  is  highly  beneficial,  the  usual  proportion  of  the  powder 
employed  is  one  measure  to  one  of  lime,  combined  with  various  pro- 
portions of  sand,  for  which  Smeaton's  rule,  that  the  latter  shall  not 
exceed  two  measures,  when  the  lime  alone,  without  the  Puzzolana, 
will  bear  three  measures  of  sand,  is  probably  the  most  judicious.  By 
our  experiments,  it  appears  that  one  measure  of  sand  to  one  of  Puzzo- 
lana powder,  and  one  of  chalk-lime  paste,  produces  the  strongest 
Puzzolana  mortar  with  that  species  of  lime ;  that  one  additional 
measure  of  sand  diminishes  the  adhesiveness  of  this  mortar  in  a  slight 
degree,  not  exceeding  10  per  cent.,  but  that  it  diminishes  the  resist- 
ance by  60  per  cent. 

4:th.  Its  effect  upon  a  strong  hydraulic  lime,  such  as  Blue  Lias  lime, 
is  to  increase  its  adhesiveness,  and  when  mixed  in  the  proportions  of 
two  measures  of  the  Puzzolana  powder  to  one  of  lime,  it  increases  its 
resistance  also,  but  one  measure  of  each  would  be  the  utmost  propor- 
tions that  could  be  recommended  in  practice. 

5th.  Its  effect  upon  a  weak  hydraulic  lime  is  favorable,  and  for 
works  under  water  it  would  not  be  prudent  to  use  such  limes  without 
an  admixture  of  It. 

M.  vicat's  rules  for  judging  of  the  quality  of  natural 

OR  ARTIFICIAL  PUZZOLANAS. 

He  recommends  testing  them  by  acids,  and  in  water,  and  observes : 
1st.  That  those  which  are  not  acted  upon  by  acids,  and  have  no  action 


PUZZOLANA. 


143 


on  lime-water,  are  inert.  2d.  That  those  which  are  moderately  acted 
upon  by  acids,  and  which  act  very  moderately  in  lime-water,  have 
little  energy.  3rd.  Those  which  are  powerfully  acted  upon  by  acids, 
and  which  are  very  active  in  lime-water,  are  energetic. 

M.  Baggi,  of  Gottenburgh,  made  use  of  a  very  hard,  black, 
schistous  rock,  which  he  burned  until  it  lost  its  hardness,  and  after- 
wards pulverized  it,  in  which  state  it  made,  when  mixed  with  lime,  a 
good  hydraulic  mortar. 

Count  Chaptal  calcined  the  ochrey  clays  of  Languedoc,  (France,) of 
which  he  made  an  excellent  artificial  Puzzolana ;  and  subsequently 
M.  Mason  experimented  upon  the  same  description  of  clay,  and  con- 
verted them  into  Puzzolanas,  which  were  tried  as  "betons,"  by  sink- 
ing casks  filled  with  them  in  the  Seine,  and  which,  after  six  months' 
submersion,  were  found  to  be  extremely  hard. 

General  Treussart  states  that  a  mixture  of  common  lime  with 
sand  and  brick-dust  (pounded  brick  is  probably  meant),  in  equal  parts, 
forms  a  hydraulic  mortar  requiring  a  breaking  weight  of  from  221  to 
331  lbs.  avoirdupoise,  which  he  considers  sufficient  for  general  pur- 
poses, but  for  more  important  works  he  thinks  that  a  resistance  of 
from  331  to  441  lbs.  is  desirable,  for  which  purpose  the  clays  suited  for 
potteries  should  be  selected,  which  are  to  be  treated  by  burning,  &c., 
as  before  described. 

He  also  remarks  that  artificial  Puzzolana,  formed  of  bricks  exposed 
to  a  draft  of  air  while  being  burnt,  will  set  in  three  or  four  days, 
whereas,  that  formed  of  similar  bricks,  equally  well  burned,  but  not  so 
exposed,  may  not  set  for  ten,  twenty,  or  even  thirty  days,  and  yet 
may  form  good  hydraulic  mortars  in  time.  He  says  that  he  has  ob- 
served, that  the  strength  of  artificial  Puzzolana  may  generally  be 
judged  by  its  quickness  in  setting. 

He  also  tried  other  experiments  upon  trdss^  and  found  that  mortar 
made  of  one  measure  of  common  lime,  mixed  with  two  measures  of 
sifted  trass,  was  nearly  twice  as  strong  as  the  mortar  made  of  the 
same  lime,  mixed  with  coarse  trass  in  the  same  proportion,  their  re- 


144 


COMPOSITION  OF  MORTAR. 


sistence  being  463  and  232  lbs.  respectively ;  and  he  also  ascertained 
that  wetting  trass  did  it  little  or  no  harm,  and  he  is  of  opinion,  that 
neither  trass  nor  any  sort  of  artificial  Puzzolana  nor  natural  Puzzolana 
can  possibly  be  injured  by  exposure  to  the  weather. 

M.  vicat's  opinion  of  the  best  combination  of  various  limes 

WITH  other  ingredients  FOR  THE  COMPOSITION  OF 
MORTAR. 

In  order  to  obtain  hydraulic  mortars  capable  of  acquiring  great 
hardness  under  water,  or  in  situations  always  moist,  he  recommends 
weak  hydraulic  limes  to  be  combined  with  energetic  Puzzolanas,  and 
that  hydraulic  limes  may  be  combined  with  Puzzolanas  of  little  energy, 
but  that  first-class  hydraulic  limes  may  be  mixed  with  inert  substances 
such  as  sand,  whether  siliceous  or  calcareous,  and  also  with  the  slag 
of  forges,  &c. 

To  obtain  mortars  or  cements  capable  of  acquiring  great  hard- 
ness in  the  open  air,  and  to  resist  rain,  heat,  and  severe  frosts,  ne  is 
of  opinion,  that  fat  limes  are  unsuited  for  such  purposes,  nor  can  weak 
hydraulic  limes  accomplish  it  in  a  satisfactory  manner,  but  that  or- 
dinary and  eminently  hydraulic  limes  will  succeed  if  mixed  with  any 
clean  sand,  quartoze  dust  or  with  the  powder  of  hard  lime-stones  or 
other  inert  substances. 

Of  mortars  to  be  used  under  water  he  says  that  the  proportions 
of  sand  and  other  ingredients  used  with  different  sorts  of  lime,  must 
vary  according  to  circumstances,  but  as  a  general  rule  he  states  that 
arenes  psammonites  and  clai/s  will  do  with  a  smaller  proportion  of  lime 
than  other  substances  generally,  for  in  measuring  them  in  the  state 
of  dry  powder,  they  require  of  fat  lime-paste,  slaked  by  the  common 
method,  from  15  to  20  per  cent ;  of  moderate  hydraulic  lime  from  20 
to  25  per  cent ;  and  of  hydraulic  lime,  from  25  to  30  per  cent.  That 
the  energetic  or  very  energetic  Puzzolanas  require,  under  the  same 
circumstances,  of  fat  lime  from  30  to  50  per  cent,  and  of  moderate 


VICAT'S  MODE  OF  MAKING  LIME. 


145 


hydraulic  lime  from  40  to  60  per  cent ;  and  that  silicious  any  calcare- 
ous sands  require  of  hydraulic  or  eminently  hydraulic  lime  from  50  to 
66  per  cent.  As  a  general  rule  it  is  better  to  err  by  using  too  much, 
than  too  little  lime  in  such  mixtures,  for  excess  of  lime  causes  them 
to  adhere  better  to  stone,  but  if  to  be  used  alone,  then  the  just  propor- 
tions attain  the  greatest  induration. 

M.  vicat's  mode  op  preparing  artificial  hydraulic 

LIMES. 

Wherever  good  hydraulic  limes  are  to  be  found  on  the  spot,  or  can 
be  procured  at  a  moderate  expense,  M.  Vicat  recommends  using 
them,  but  when  only  common  limes  or  inferior  hydraulic  limes 
are  to  be  found,  he  converts  them  into  water-setting  limes,  by  the  fol- 
lowing process: — 

Burn  the  lime  in  the  usual  manner,  and  let  it  slake  or  fall  down 
into  powder  by  spontaneous  slaking  in  the  air  under  cover,  then  mix 
the  slaked  lime  with  a  certain  quantity  of  gray  or  brown  clay,  or  sim- 
ply with  brick  earth  into  a  paste  with  water,  and  form  it  into  balls, 
which  are  to  be  first  dried  and  then  baked  in  a  kiln.  He  gives  the 
following  proportions  of  clay  to  be  used  . — 

Very  fat  common  limes,  such  as  absorb  a  great  quantity  of  water 
in  slaking,  and  which  are  pure  or  nearly  so,  as  common  chalk,  will  bear 
20  per  cent  of  clay ;  for  middling  limes  15  per  cent  is  enough,  but  for 
limes  having  hydraulic  properties  10  or  even  6  per  cent  may  suffice. 
When  the  proportion  of  clay  is  increased  to  33  or  40  per  cent,  the 
lime  obtained  does  not  slake,  but  it  is  easily  pulverized,  after  which 
when  moistened,  it  forms  a  paste  which  sets  very  quickly  under  water. 
When  the  clay  is  mixed  V^ith  stones  or  gravel,  it  must  be  washed,  and 
the  fluid  mixture  stirred  up  and  made  to  flow  over  the  vessel  into  an- 
other receptacle  to  subside ;  and  when  sufficiently  dry,  mix  the 
liquid  clay  with  slaked  lime  powder,  in  which  state  it  will  be  found 
more  convenient  than  if  it  were  stiffer. 


7 


146 


ROOFS  AND  FLOORS. 


RESULTS  AND  INTEREWCES  OBTAINED  FROM  EXPERIMENTS, 

From  the  experiments  on  lime  and  lime  mortars  (before  de- 
scribed), combined  with  those  previously  tried  on  cement,  the  follow- 
ing inferences  may  be  drawn : — 

1st.  Of  the  effects  of  sand  and  of  Puzzolana  on  cement.  Sand 
in  all  cases  dimishes  the  strength  of  cement,  whether  as  estimating 
its  adhesiveness,  its  resistance  or  its  water  setting  powers.  Puzzolana 
is  still  more  injurious  to  it  than  sand,  as  was  found  by  a  series  of  ex- 
periments to  ascertain  this  point.  In  short  every  extraneous  sub- 
stance, excepting  the  carbonate  of  magnesia,  which  is  far  too  expen- 
sive to  use  for  building  purposes  in  this  country,  (found  abundantly  in 
one  part  of  India,  and  consequently,  cheap)  injures,  and  when  added 
in  a  certain  excess,  entirely  ruins  cement. 

2ndly.  Of  the  effects  of  sand  on  common  chalk  lime,  or  weak 
hydraulic  limes,  such  as  the  Hailing  lime.  Sand  appears  rather  to 
diminish  the  adhesiveness  of  chalk  lime,  but  slightly  to  increase  that 
of  Hailing  lime,  in  either  case  the  difference  being  insignificant.  Its 
effect  upon  their  resistence  is  more  marked,  especially  upon  that  of 
chalk  lime,  which  it  nearly  doubles,  whilst  it  only  increases  that  of 
Hailing  lime  by  one-half. 

3rdly.  Of  the  effects  of  sand  on  strongly  hydraulic  limes,  such  as 
the  blue  lias.  It  appears  to  increase  both  their  adhesiveness  and 
their  resistance  in  a  slight  degree,  and  blue  lias  lime  does  not  appear 
to  be  materially  injured  by  an  admixture  of  three  parts  of  sand  to 
one  of  lime,  although  two  of  sand  to  one  of  lime  is  found  to  make 
the  best  mortar. 


ON  THE    CONSTRUCTION  OF  WATER-TIGHT  ROOFS 
AND  FIRE-PROOF  FLOORS. 
Water-tight  roofs  are  constructed  with  two  or  three  courses  of  plain 
tiles,  which  are  about  lOJ  inches  long,  6 J  broad,  and  f  of  an 
inch  thick,  and  weigh  about  2  J  lbs.  each  ;  they  are  laid  in  cement 


ROOFS  AND  ELOORS. 


147 


upon  flat  beams  or  rafters,  placed  about  4  feet  apart,  crossed  by  trans- 
verse battens,  2  inches  by  three  inches,  at  intervals  of  11  inches,  from 
centre  to  centre;  the  joints  of  each  course  of  tiles  are  broken,  and  the 
upper  covering  should  be  about  an  inch  thick.  The  roof  must  have 
sufficient  fall  to  carry  off  the  rain,  &c.,  and  if  iron  bearers  are  substi- 
tuted for  timber,  it  would  be  better. 

Mr.  Frost  contrived  an  ingenious  method  of  forming  fire-proof 
floors  and  roofs  with  square  earthenware  tubes  measuring  external- 
ly 2 J  inches  square  and  1.  foot  long.  Two  courses  of  these  were 
laid  in  pure  cement  at  right  angles  to  each  other,  and  formed  a  floor 
from  8  to  10  feet  wide,  and  which  was  considered  safe  for  any  number 
of  persons  to  walk  upon.  In  consequence  of  its  tubulated  form  it  is 
reckoned  much  stronger  than  if  made  of  plain  tiles,  or  any  sort  of 
plain  flat  tiles  of  equal  weight.  The  tubes  are  so  arranged  as  to  break 
joint  with  one  another  in  both  courses,  and  a  coat  of  cement  stucco  is 
applied  both  above  and  below,  which  completes  and  strengthens  it- 
They  are  turned  in  flat  arches  on  iron  beams  or  bearers,  at  8  or  10 
feet  apart. 

Fire-proof  ceilings  or  roofs  are  constructed  in  like  manner  with  arch 
pots,  which  are  made  square  at  top  and  round  at  bottom,  the  side  of 
the  upper  square  and  the  diameter  of  the  lower  circle  being  equal,  4 
f  inches,  and  from  5|  to  8  inches  high,  having  the  sides  and  bot- 
tom screwed,  and  a  small  hole  in  the  top  to  receive  the  cement  and 
form  a  key  thereto :  the  smaller  ones  weigh  about  2 1  lbs.,  and  the 
larger  about  4J  lbs. 

Ceilings  of  this  description  were  formed  over  the  basement  of  the 
Treasury  buildings,  Whitehall,  at  Buckingham  Palace,  the  Senior 
United  Service  Club,  and  the  National  Gallery,  London.  Various 
experients,  such  as  pieces  of  bricks,  or  half  pots  broken  down  the 
middle,  alternating  with  the  regular  arch-pots,  were  used,  in  order  to 
obtain  proper  bond  at  the  springing  of  the  arches,  which  generally 
abutted  against  stone  skew-backs,  on  each  side  of  the  iron  girders, 


148 


MEASUREMENT  OF  LIME. 


which  were  placed  usually  about  6  feet  apart,  seldom  more  than  7i 
feet,  and  never  less  than  4J  feet,  and  their  rise  seldom  exceeded  6 
inches. 


ON  THE  MEASUREMENT  OF  LIME. 

Lieut.-Col.  Pasley  found,  by  experiment,  that  a  very  important  difference 
in  the  apparent  quantity  of  lime  (and  coals)  exists  under  various  con- 
ditions, particularly  in  reference  to  the  size  of  the  lumps  or  particles 
thereof,  and  it  being  of  the  utmost  importance  for  both  the  interest  of 
trade  and  purposes  of  experiment  to  ascertain  and  determine  the  real 
quantity  contained  in  any  apparent  measure,  he  devoted  much  time 
and  study  to  the  subject  which  resulted  in  the  following  facts : — 

1st.  He  found  that  1  cubic  foot  of  solid  coal  was  broken  into  about 
30  pieces,  together  with  the  rubbish  and  dust  produced  in  the  break- 
ing, occupied  2  J  cubic  feet  of  fair  level  measure,  but  that  on  further 
breaking  the  same  coal  into  a  tythe  part  of  the  size,  or  300  pieces, 
which  produced  a  greater  quantity  of  rubbish,  it  filled  If  foot ;  but 
on  being  pounded  entirely  into  rubbish  and  dust,  it  only  filled  1  J 
cubic  foot.  He  also  found  that  a  compact  10  cubic  feet  measure  con- 
tained a  greater  quantity,  by  about  5  per  cent.,  than  ten  times  the  con- 
tents of  a  single  cubic  measure,  in  all  which  states  the  real  quantity 
of  the  coal  was  the  same,  though  the  estimates  of  it  by  measure  were 
so  very  difierent ;  and  as  lime  is  usually  sold  by  the  same  measure,  the 
difierence  of  the  actual  quantity  supplied  would,  in  like  manner  as  with 
coals,  vary  in  proportion  to  the  size  of  the  component  parts  of  a  cubic 
foot,  cubic  yard,  or  any  other  measure,  so  that  for  the  purposes  of  use 
in  building,  or  for  experiment,  great  deception  and  error  may  arise 
He  further  observes,  however,  that  this  difference  in  the  uncertainty 
of  measure  is  not  so  great  in  lime  as  in  coals,  inasmuch  that  the  pieces 
of  lime-stone  are  necessarily  obliged  to  be  broken  into  one  uniform 
size  for  the  convenience  of  burning,  and  accordingly  the  builder,  in 


MEASUREMENT  OF  LIME. 


149 


purchasing  his  lime  in  lumps,  by  the  cubic  yard,  may  depend  upon 
receiving  nearly  the  same  average  quantity  of  the  same  sort  of  lime 
from  the  same  kiln ;  the  variation  of  different  sorts  of  lime  from  dif- 
ferent kilns  seldom  exceeds  10  per  cent.,  the  excess  of  real  quantity 
being  in  favor  of  small  pieces  of  kiln-burned  lime,  about  9  cubic  yards 
of  which  will  equal  10  cubic  yards  of  the  same  sort  of  lime,  when 
burned  in  a  flame  kiln. 

DIFFERENT  MODES  OF  MEASURING  LIME. 

1st.  In  lumps  as  it  comes  from  the  kiln.  This  is  the  customary 
mode,  which,  if  any  large  compact  measure,  such  as  one  containing  a 
cubic  yard,  or  even  10  cubic  feet  only,  be  used,  will  afford  a  tolerable 
fair  estimate  of  the  quantity,  but  not  so  if  much  smaller  measures  be 
used. 

2d.  In  slaked  lime  powder.  This  mode  was  first  adopted  by  Smea- 
ton,  at  the  building  of  the  Eddystone  lighthouse,  and  recommended 
by  him  for  all  hydraulic  mortars ;  and  the  term  applies  to  lime  broken 
small  and  slaked  by  a  moderate  quantity  of  water,  sprinkled  over  it 
with  a  watering  pot,  after  which  it  should  be  covered  up,  until  it  falls 
down  into  a  powder,  for  which  more  or  less  time  will  be  required,  ac- 
cording to  the  quality  of  the  lime,  but  from  18  to  24:  hours  will  be 
sufficient,  as  even  the  blue  lias  limes,  which  are  the  slowest  slaking  of 
all  our  English  limes,  from  possessing  the  strongest  hydraulic  proper- 
ties, do  not  usually  require  more  than  18  hours. 

3d.  In  quick-lime  powder.  For  this  purpose  the  lime  is  reduced  to 
a  fine  powder,  by  being  pounded  in  a  mill,  or  by  manual  labor ;  this 
mode,  is,  however,  but  seldom  adopted. 

4th.  In  slaked  lime  putty  or  paste,  This  mode  was  adopted  in 
preference  by  Col.  Pasley  in  his  experiments  at  Chatham,  and  applies 
to  quick-lime  fresh  from  the  kiln,  pounded  in  a  mortar,  and  after- 
wards thoroughly  slaked  with  a  moderate  quantity  of  water,  gradually 
applied,  until  the  lime,  throwing  out  more  or  less  heat,  shall  become 


150 


LIMEKILNS. 


quite  cool,  and  then  re-mixing  it  with  more  water  into  a  stifilsh  paste, 
in  which  state  it  is  to  be  measured. 

Lime  in  lumps,  as  in  the  first  case,  is  always  computed  by  fair  leyel 
measure,  rather  full  than  otherwise.  Lime  in  powder,  as  in  the  second 
and  third  cases,  is  reckoned  by  strike  measure.  In  the  fourth  case, 
of  putty  or  paste,  it  is  also  measured  in  the  latter  mode.  A  more  ac- 
curate method  of  ascertaining  the  quantity  of  lime  would  be  by  weigh- 
ing it,  provided  it  be  well  burned  and  fresh  from  the  kiln. 

The  average  weight  of  well  burned  blue  lias,  Hailing,  and  chalk- 
lime,  when  well  burned  and  broken  into  rather  small  pieces,  suited  to 
the  common  lime-kiln,  may  be  estimated  at  49,  37  and  31 J  lbs. 
per  cubic  foot,  respectively. 


A  MODERN  LIME  KILN. 

As  an  example  of  a  modern  lime-kiln  of  the  most  approved  form 
and  construction,  with  a  full  description  of  the  structure,  and  of  the 
modus  operandi  of  lime-burning,  a  better  cannot  be  selected  than  that 
given  by  Mr.  Samuel  Clegg,  Junr.  (of  London),  in  his  "Notes  on 
Construction,"  published  November,  1851,  which  is  now  quoted  with 
the  illustration,  for  the  advantage  and  interest  of  all  concerned  in  the 
trade. 

iVide  plates  at  end  of  book.] 
ON  THE  BURNING  OF  LIMESTONE. 

In  England  the  operation  of  calcination  is  left  almost  entirely  to 
the  lime-burner,  and  the  engineer  receives  his  material  in  the  state  of 
quick-lime,  the  virtue  of  which  is  generally  so  well  known,  that  he 
mixes  it  up  for  extensive  use  without  previous  trial  of  its  virtues. 
This,  however,  would  not  be  the  case  in  new  countries,  or  in  those 
districts  removed  from  spots  where  lime-burning  is  carried  on  as 
a  trade ;  he  must  then  be  his  own  lime-burner,  and  the  knowledge  of 
the  best  processes  followed,  both  as  to  fuel  and  form  of  kiln,  must  be 
studied  by  him. 


LIMEKILNS. 


151 


The  art  of  lime-burning  consists  in  calcining  the  greatest  quantity 
of  material  with  the  least  expendituie  fuel,  of  time  and  of  manual 
labor.  To  gain  this  end,  the  preparation  of  the  lime-stone  its  ar- 
rangement in  the  kiln,  the  disposition  of  the  fuel,  the  regulation  of  the 
heat  and  draught,  and  the  proper  coloring  of  the  lime  must  be  attended 
to.  The  general  process  will  probably  be  more  easily  understood  by 
first  giving  a  description  of  a  kiln  and  the  manipulation  necessary, 
and  then  proceeding  to  more  minute  matters. 

THE  KILN. 

The  kiln  shown  in  the  wood-cut  called  a  "flare  or  dome  kiln," 
is  used  by  the  most  extensive  lime-burners  in  Dorking,  and  is  similar 
to  all  those  used  in  the  vicinity  of  London,  only  they  are  sometimes 
placed  in  pairs  or  three  or  four  together ;  this  arrangement,  by  expos- 
ing a  less  surface  of  wall  to  the  cold  air,  slightly  diminishes  the  expendi- 
ture of  fuel ;  but  is  probably  adopted  more  with  a  view  of  saving  labor 
than  fuel,  as  the  fireman  has  all  the  fires  under  his  immediate  control. 
The  interior  of  the  kiln  is  of  a  circular  bottle  shape,  the  diameter  at 
the  bottom  being  10  feet  6  inches,  the  wall  is  carried  up  plumb  to  a 
height  of  7  feet,  at  which  point  the  dome  is  commenced,  which  closes 
in  the  kiln,  leaving  only  an  opening  at  the  top  1  foot  8  inches  dia- 
meter and  2  feet  high  as  a  chimney ;  the  total  height  from  the  hearth 
to  the  top  of  the  chimney  being  19  feet  6  inches.  The  thickness  of  the 
brickwork,  to  a  height  of  11  feet,  is  14  inches,  which  is  the  level  of  the 
top  of  a  surrounding  wall  of  rubble  work ;  from  this  height  to  the  top, 
the  thickness  is  nine  inches,  including  the  lining  of  fire-brick. 
The  surrounding  wall  is  of  a  horse-shoe  form,  the  circular  part  20 
feet  in  diameter,  and  the  depth  from  front  to  back  19  feet ;  it  is  about 
18  inches  thick,  batters,  about  6  inches,  and  the  space  between  it  and 
the  brickwork  of  the  kiln,  is  filled  in  with  rubbish.  At  the  back  of 
the  kiln  and  3  feet  6  inches  above  the  grate  bars,  a  doorway  is  made,  6 
feet  6  inches  high,  and  4  feet  8  inches  wide,  arched  over  with  9 
inches  brick-work,  through  which  the  kiln  is  filled.    On  the  opposite 


152 


LIMEKILNS. 


side  to  this  opening  are  two  furnace  doors,  the  grates  18  inches  wide,  ex* 
tending  to  the  back  of  the  kiln.  The  furnace  mouths  are  funnel  shaped, 
and  are  3  feet  6  inches  high  above  the  grates  in  the  inside.  This 
construction  makes  it  convenient  for  turning  the  rough  arches  of  the 
limestone  when  filling  the  kiln.  A  shed  is  built  on  this  side  to 
protect  the  workmen  and  the  fuel  from  the  weather. 

CHARGING  THE  KILN. 

In  charging  the  kiln,  brushwood  is  laid  over  the  grates,  with  a 
stratum  of  coals  upon  it  to  form  the  fire.  Large  lumps  of  lime- 
stone, or  chalk,  are  then  brought  in  at  the  door-way,  and  a  rough 
arch,  about  3  feet  high  and  2  feet  wide,  is  firmly  built  over  each  grate, 
that  the  superincumbent  weight  of  the  stone  may  not  crush  them.  The 
lumps  are  generally  trimmed  to  shape  that  they  may  bed  properly 
upon  these  arches.  The  general  mass  of  stone  to  be  burnt  is  then 
thrown  in,  care  being  taken  to  keep  the  largest  stones  at  the  bottom, 
and  where  the  greatest  heat  will  be,  and  gradually  to  diminish  the 
size  towards  the  top,  where  the  small  pieces  are  placed.  The  top  of 
the  charge  is  about  on  a  level  with  the  surrounding  rubble  wall. 
Some  care  is  taken  to  have  the  interstices  between  the  lumps  of  stone 
as  large  as  possible,  by  placing  the  angles  in  contact ;  the  object  of 
this  is  to  facilitate  the  calcination  of  the  large  lumps,  for  if  the  smaller 
pieces  were  mixed  with  larger,  they  would  be  *^  over-burnt"  *  before 
the  latter  were  nearly  calcined  ;  there  is  a  greater  draught  also  when 
the  spaces  between  the  stones  are  greater,  and  this  likewise  assists  to 
burn  the  large  lumps  as  quickly  as  the  small.  When  compact  lime- 
stone is  to  be  burnt,  it  should  be  broken  into  pieces  not  exceeding  a 
fist  in  size.    Chalk  lumps  may  be  much  larger.    If  the  stones  are 

*  Pure  lime  is  incombustible,  and  therefore  cannot  be  over-bnrnt,  but  lime 
containing  the  impurities  necessary  to  render  it  a  weather  lime,  easily  fuses  and 
becomes  covered  with  a  kind  of  enamel ;  it  slakes  with  gi-eat  difficulty,  sometimes 
it  will  not  slake  at  all,  but  becomes  reduced  to  a  harsh  powder,  altogether  in^t^ 
and  is  called  dead  lirae. 


LIMEKILNS. 


153 


broken  into  too  small  pieces,  the  spaces  between  them  will  not  give 
free  passage  enough  to  the  draught  and  flame.  The  stone  thro\m 
into  the  kiln  should  not  be  too  dry :  its  state  just  as  taken  from  the 
quarry  is  the  best ;  if  it  has  lost  much  of  its  natural  moisture  by  lying 
by.  Water  should  be  sprinkled  over  it  with  a  rose.  The  reason  of 
raoistm'e  being  useful,  is,  that  the  vapor  from  it  facilitates  the  disen- 
gagement of  the  carbonic  acid  gas,  by  reason  of  its  great  affinity  for 
water ;  the  stones,  however,  must  not  be  wet. 

THE  BUKNING. 

In  commencing  the  operation  of  burning,  the  fire  must  be  lighted, 
and  the  heat  of  tlie  kiln  very  gradually  raised;  from  15  to  20  hours 
being  suffered  to  elapse  before  the  whole  intensity  of  the  fuel  and 
draught  is  allowed  to  be  felt.  To  keep  the  fire  down,  as  little  air  as 
possible  must  be  allowed  to  pass  through  the  grate  bars ;  and  if  there 
are  not  shutters  or  dampers  to  the  ash-pits,  lumps  of  stone  may  be 
built  up  before  them,  to  be  gradually  removed  as  greater  draught  is 
required.  The  effect  of  raising  the  heat  too  suddenly  would  be  to 
destroy  the  rough  arches  over  the  grates,  when  the  mass  above  them 
would  fall  and  smotlier  the  fire ;  also  the  lumps  of  stone  would  splin- 
ter, and  the  splinters  fillhig  the  air  spaces  between  them  would  de- 
stroy the  draught.  This  attention  to  the  gentle  increase  of  the  heat 
is  more  especially  necessary  in  a  new  kiln,  when  the  sudden  heat 
would  burst  the  green  work ;  hooping  the  kiln  with  iron,  to  prevent 
this  kind  of  danger,  is  therefore  practiced.  When  the  calcination  is 
complete,  the  color  of  the  flame  from  the  chimney  will  be  either  of  a 
pale,  yellow  or  a  white,  with  no  smoke ;  the  stone  in  the  kiln  ^\t11 
have  settled  down  to  an  extent  of  a  fifth  or  a  sixth  of  the  entire  mass, 
and  the  whole  will  present  a  glowing  red  heat,  or  a  whitish  rosy  tint. 
The  experienced  lime-burnei  well  knows  by  these  indications  that 
his  charge  is  worked  out ;  but  those  who  have  not  had  much  practice, 
should  take  out  a  piece  of  the  stone  from  the  kiln,  remove  the  outer 
coating,  and  slake  the  inside  portion  in  water;  if  no  effer- 


154 


LIMEKILNS. 


veecence  ensues  upon  the  applicatioa  of  an  acid  having  a  stronger 
aflSnity  for  the  base  than  the  carbonic  acid  (nitric  or  sulphuric  acid, 
for  instance),  the  calcination  is  complete.  When  this  is  ascertained 
to  be  the  case,  the  fire  may  be  raked  out,  and  the  kiln  suffered  to  cool 
gradually.  If  the  ash-pits  and  air-vents  are  closed,  the  effect  will  be 
favorable  to  the  lime,  which  will  be  harder,  and  will  keep  longer  ex- 
posed to  the  air,  so  that  it  can  be  conveyed  to  greater  distance  with- 
out deterioration ;  but  for  a  long  journey,  or  if  the  lime  is  not  to  be 
used  for  some  time,  it  should  be  put  into  tight  casks. 

A  flare  kiln,  containing  45  yards  of  Dorking  gray  chalk  takes  48 
hours  to  burn,  and  consumes  about  7  tons  of  coal,  the  quantity  de- 
pending somewhat  upon  the  dryness  of  the  chalk,  but  the  varia- 
tion is  very  inconsiderable,  never  exceeding  five  or  six  sacks  (10  or  12 
cwt.) 

The  cost  of  such  a  kiln  of  lime  is  about  the  following : — 

f,         7  American 

i-  S.  a.  Currency. 

Blasting  and  digging  in  the  quarry,       .       .       0  1 2  0  or  $2  88 

Carting  (dependent  on  the  distance)  say    .       .    0  10  6  2  52 

Turning  rough  arches,  and  filling,         .       .       0  16  0  3  84 

Labor  for  burning,                                            0  18  0  4  32 

Emptying  at  Sd,  per  cubic  yard,    .       .       .       0  11  3  2  70 


£3    7  9  or  $16  26 

To  this  must  be  added  the  price  of  seven  tons  of  coal  used  as 
fuel,  and  the  value  of  the  land  from  which  the  limestone  is  taken. 
The  price  in  London  for  Dorking  lime  is  ten  shillings  per  cubic  yard, 
or  $2.40. 

A  kiln  in  constant  use  v/ill  not  last  more  than  eighteen  months 
or  two  years,  without  it  be  re-lined.  It  is  economy,  therefore,  to  use 
the  best  Stourbridge  bricks  or  other  fire-bricks,  set  in  fire-clay,  in  the 
original  construction. 

In  selecting  a  position  for  the  kiln,  the  spot  should  be  chosen  as 
near  to  the  quarry  as  possible,  for  as  the  stone  loses  about  45  per  cent 


CEMENT  KILNS. 


155 


in  burning,  it  is  a  saving  in  the  carriage  of  the  remaining  55  per  cent. 
A  sloping  bank  should  also  be  chosen,  that  the  natural  ground  may 
be  on  a  level  at  the  back  of  the  bottom  of  the  hatchway,  and  at  the 
front  with  the  bottom  of  the  ash-pits. 


DESCRIPTION  OF  THE  CEMENT  KILN  USED  AT 
SHEERNESS  DOCKYARD. 

The  form  differs  in  nothing  from  the  inverted,  conical  frustum- 
shaped  lime-kilns ;  and  the  size  may  be  varied  according  to  circum- 
stances ;  but  when  not  built  upon  the  side  of  a  cliff  or  hill,  as  is 
usually  the  case,  they  are  sometimes  built  in  the  external  form  of 
small  cylindrical  brick  towers,  with  strong  iron  hoops,  and  sometimes 
also  with  vertical  bars,  to  prevent  tb  .i  fire  splitting  the  brickwork. 

The  kiln  designed  and  built  by  Mr.  Rennie,  C.  E.,  at  Sheemess 
dockyard  (and  which  is  considered  of  a  very  convenient  construction) 
is  a  mass  of  brickwork,  measu  ing  17  feet  in  external  diameter  and 
21  J  feet  in  extreme  height.  The  hollow  inverted  conical  frustum 
is  8  feet  clear  diameter  at  top  and  5  J  feet  at  bottom,  a  9-inch  ring 
of  brickwork  incloses  this  space,  surrounded  by  the  brickwork  in  mass. 
At  the  bottom  of  it  there  is  a  sort  of  small  solid  dome,  2  feet  3  inches 
high,  for  the  purpose  of  throwing  off  the  calcined  cement,  and  to 
cause  it  to  fall  down  through  the  ash-holes  of  four  openings,  or 
**eyes,"  as  they  are  technically  termed,  at  the  bottom  of  the  kiln, 
formed  in  recesses  which  are  arched  over,  and  increased  to  6  feet  3 
inches  in  width,  and  7  feet  6  inches  in  height,  at  the  outside.  These 
ash-holes  are  2  feet  6  inches  wide,  and  1 8  inches  high  to  the  crown 
of  the  flat  arch  which  covers  them,  and  over  each,  at  the  interval  of 
15  inches  higher,  there  are  fire-holes  12  inches  square,  within  the 
same  recesses,  having  iron  bars  at  top,  to  support  the  brickwork  above 
them. 


156 


CEMENT  KILNS. 


Plate  2  (see  end  of  the  book),  Figs.  1,  2  and  3,  represents  the  con- 
struction of  the  above-described  kiln,  with  the  exception  of  the  paror 
pet  wall  or  railing  which  is  attached  around  the  top  of  the  kiln  to  pre- 
vent the  workmen  falling  over. 

There  are  four  wrought  iron  hoops  inclosing  the  brickwork,  as 
shown  in  Eig.  2,  each  3  inches  wide,  and  3-8  of  an  inch  thick,  which 
are  formed  in  several  pieces,  connected  together  at  the  joints  by  strong 
vertical  iron  bolts,  similar  to  a  hinge.  The  plan,  Eig.  3,  represents  a 
horizontal  section,  taken  on  the  level  of  the  ash-holes  (or  eyes),  in 
which  the  voids  are  left  blank  and  the  solid  parts  shaded.  This  kiln 
will  contain  nearly  30  tons  of  broken  cement-stone,  averaging  26  cubic 
feet  to  the  ton,  exclusive  of  the  fuel  necessary  to  burn  the  cement 
stone. 

THE  OPERATION  OF  BURNING. 

The  bottom  of  the  kiln  is  first  filled  with  shavings  and  wood,  after 
which  the  coals  and  cement-stone  are  added  in  alternate  layers,  the 
former  being  broken  so  small  that  they  occupy  little  more  space  than 
necessary  to  fill  the  interstices  betAveen  the  strata  of  the  latter,  each 
of  which  is  usually  one  foot  in  height  or  thickness. 

Three  days  after  the  kiln  is  lighted,  the  calcined  cement  should  be 
drawn,  whilst  laying  on  more  coals  and  raw  cement-stone  at  the  top, 
so  as  to  keep  it  continually  burning ;  the  kiln  may  be  drawn  every 
twenty-four  hours.  Each  ton  of  cement-stone  produces  about  about 
21  bushels  of  cement-powder. 

Sometimes  two  such  kilns  are  built  near  to  each  other,  and  con- 
nected by  a  bridge  at  top,  and  a  crane  or  derrick  fixed  there  to  raise 
the  cement-stone  and  fuel,  and  to  deposit  it  where  and  when  required. 
It  is  not  always  customary  to  make  the  inclosing  brickwork  so  thick 
as  before  described,  but  the  width  at  the  top  is  increased  by  a  project- 
ing balcony,  the  ascent  to  which  is  by  an  outside  stairway. 

Mr.  Mitchell  recommends  the  introduction  of  chains  in  addition  to 
the  external  hoops,  the  better  to  resist  the  tendency  of  the  fire  to  split 


AETIEICIAL  CEMENT. 


157 


the  brick-work ;  and  Col.  Pasley  suggests  a  kiln  of  the  form  shown  in 
Plate  3,  which  is  a  vertical  section  thereof.  It  is  of  rather  an  oval 
form,  instead  of  the  inverted  frustum  of  a  cone,  having  its  greatest 
diameter  some  little  distance  from  the  top ;  this  kiln  is  of  the  same 
height  as  the  one  before  described,  and  of  the  same  diameter  at  bot- 
tom, and  from  thence  increasing  to  8  feet  at  about  two-thirds  of  the 
way  up,  and  again  diminishing  to  6  feet  in  clear  diameter  at  top. 

The  calcined  cement  is  afterwards  to  be  ground  in  a  proper  mill, 
and  passed  through  dressing  sieves  similar  to  flour,  and  immediately 
packed  in  tight  casks  or  bags  for  use. 


RULE  FOR  MAKING  AN  ARTIFICIAL  CEMENT,  WHEN 
HARD  LIME-STONE  ONLY  CAN  BE  PROCURED. 

Supposing  that  no  chalk  can  be  procured,  but  only  hard  lime-stone, 
which  must  be  bm-ned  and  slaked  before  it  is  mixed  with  the  clay,  as 
it  would  be  too  expensive  to  grind,  and  supposing  further  that  it  is  as 
hard  as  marble  (or  nearly  a  pure  carbonate  of  lime),  the  same  propor- 
tion of  chalk  to  clay,  by  weight,  which  made  the  best  cement  mixture 
will  also  fix  the  proportion  of  lime-stone  to  the  clay ;  but  instead  of 
weighing  the  former  in  its  natural  state,  it  will  be  better  to  weigh  it 
as  quick-lime  after  it  comes  from  the  kiln,  in  which  state  40  lbs.  of 
lime  to  100  lbs.  of  blue  clay,  or  30  lbs.  of  lime  to  1  cubic  foot  of 
clay,  because  the  best  proportion  of  chalk  or  natural  lime-stone  to  the 
blue  clay,  by  weight,  is  as  100  to  137  2,  and  the  produce  of  100  lbs. 
of  pure  carbonate  of  lime  is  only  about  55  J  lbs.  of  quick-lime,  but 
as  55  is  to  137  J,  so  is  40  to  100  nearly,  which  last  proportion 
has  been  chosen  as  the  more  simple  and  easily  remembered.  Again, 
as  40  is  to  100,  so  is  30  to  97  J  nearly ;  the  last  number  being  the 
weight  in  pounds  of  one  cubic  foot  of  fresh  blue  clay;  or  39  lbs.  of  lime 
to  one  cubic  foot  of  this  clay,  wiU  be  the  proper  proportion.  Let  there- 


158 


ARTIFICIAL  CEMENT. 


fore,  the  lime,  fresh  from  the  kiln,  be  weighed  in  portions  of  39  lbs., 
and  mixed  with  sufficient  water  to  form  lumps  of  lime-paste,  of  a 
thinnish  consistency,  and  in  about  twenty-four  hours  afterwards,  mix 
each  of  these  lumps  with  one  cubic  foot  of  the  blue  clay,  and  the  whole 
incorporated  with  a  pug  mill ;  after  which,  the  process  of  making 
the  mixture  into  balls,  and  drying,  burning,  and  grinding  will  be  the 
same  as  in  working  with  chalk-paste  and  clay. 

It  will  require  one  measm*e  of  coals  for  burning  eight  measures  of 
the  raw  cement  baUs 


RULES  FOR  MAKING  AN  ARTIFICIAL  CEMENT  EQUAL 
TO  THE  BEST  NATURAL  WATER  CEMENTS 
OF  ENGLAND. 

1st.  The  ingredients :  White  or  upper  chalk  of  the  geologists, 
which  is  one  of  the  purest  carbonates  of  lime,  and  which  is  always  in- 
termixed with  a  thin  strata  or  nodules  of  flint.  These  must  be  separa- 
ted, and  the  chalk  either  ground  dry  to  an  impalpable  powder,  or,  by 
the  aid  of  water,  reduced  to  an  impalpable  paste.  Marly,  or  impure 
chalk,  usually  found  near  the  surface  of  the  ground,  must  be  re- 
jected. 

Blue  alluvial  clay  of  lakes  or  rivers,  in  a  state  of  minute  division, 
and  free  from  sand,  procurable  from  rivers  of  moderate  rapidity;  the 
brown  surface  with  which  alluvial  clay  is  usually  covered  must  be  re- 
jected ;  and  care  must  be  taken  that  the  clay  does  not  become  stale 
by  exposure  to  air,  which  gradually  destroys  its  color  and  robs 
it  of  its  virtue  as  an  ingredient  for  a  water-cement.  Where  al- 
luvial clay  is  not  to  be  had,  fine  pit  clay  wiU  answer  the  same 
purpose. 

The  clay,  if  not  required  for  immediate  use,  should  be  preserved 
in  compact  iron  vessels,  of  a  cubical  form,  closely  pressed  in,  and 
covered  with  a  little  water,  to  exclude  the  air  and  keep  it  moist. 


ARTIFICIAL  CEMENT. 


159 


2d.  Proportions  of  the  ingredients :  The  best  proportion  is  100 
lbs.  of  pure  chalk,  perfectly  dry,  mixed  with  137  J  lbs,  of  fresh  blue 
alluvial  clay,  being  equivalent  to  C  4,  B  5.5,*  which  proved  the  strong- 
est ot  all  our  experimental  artificial  cement  mixtures ;  or  if  by  meas- 
ure, 1  cubic  foot  chalk  paste,  reduced  to  the  consistence  of  stiff  mortar, 
mixed  with  1  i  cubic  foot  of  fresh  alluvial  clay ;  the  required  con- 
sistency will  be  obtained  by  mixing  1  lb.  of  dry  chalk-powder  with  7 
I  cubic  inches  of  water,  which  will  produce  18  cubic  inches  of  paste, 
as  required ;  so  that  there  will  be  96  lbs.  of  dry  chalk  to  every  cubic 
foot  of  paste.  But  these  proportions  are  subject  to  variation  according 
to  the  nature  or  quality  of  the  several  materials,  and  which  can  only 
be  determined  by  actual  experiment. 

3d.  Mode  of  grinding  the  chalk :  It  must  first  be  broken  into 
small  pieces,  and  then  ground  with  water  in  a  wash  mill  (such  as  used 
by  whitening-makers),  or  in  a  mortar  mill  (pug  mill),  both  of  which 
being  in  common  use  are  doubtless  well  known  to  our  readers. 

4th.  Mode  of  mixing  the  chalk  and  clay :  The  former,  when  ground 
with  water  in  one  of  the  mills  just  described,  would  probably  be  in  too 
fluid  a  state  for  immediate  use.  The  superfluous  water  must  there- 
fore be  partly  drained  ofif,  and  partly  evaporated,  by  allowing  it  to 
drain  under  cover  from  the  weather,  until  the  chalk-paste  is  brought 
to  a  proper  consistency ;  but  if  too  dry,  water  must  be  added  as  re- 
quired. It  must  be  then  mixed  with  the  blue  clay,  by  means  of  a 
couple  of  small  measures,  the  capacity  of  which  must  be  as  1  to  1  i, 
the  former  for  measuring  the  chalk-paste  and  the  latter,  the  clay ;  the 
contents  of  which  must  be  alternately  emptied  upon  each  other  into 
the  pug  mill,  until  it  is  quite  full ;  then  set  the  mill  in  motion,  and 
pass  the  contents  through,  which,  if  not  perfectly  incorporated  together 
by  the  first  operation,  must  be  passed  through  a  second  time.  The 
measures  used  should  be  of  a  convenient  size,  neither  too  small  nor 
too  large. 

•  Note.    C  signifies  best  class  chalk-lime,  and  B  the  blue  liaa  clay. 


% 


160 


QUALITIES  OF  CEMENT. 


6th.  Mode  of  preparing  the  raw  cement  for  the  kiln :  After  pass- 
ing through  the  pug  mill,  the  raw  cement  mixture  must  be  made  up 
into  balls  of  about  2  3  inches  diameter,  by  the  hands,  which  can  be 
performed  by  women  or  children.  The  balls  must  be  allowed  to  dry, 
so  as  not  to  stick  together  when  in  contact,  nor  to  be  easily  crushed 
by  the  superincumbent  weight  to  which  they  will  afterwards  be  ex- 
posed in  the  kiln,  for  which  purpose  48  hours*  exposure  to  the  air 
under  cover  will  probably  suffice. 

Balls  of  a  smaller  size  would  be  liable  to  spoil  by  exposure,  and 
larger  ones  would  not  be  so  convenient  for  burning. 


VARIOUS  RULES  FOR  TESTING  THE  QUALITIES  OF 
CEMENTS. 

1st.  Rule  for  judging  whether  the  cement  supplied  by  a  manufac- 
turer is  in  a  proper  state  for  use : — 

Mix  up  the  cement-powder  with  water  and  make  four  or  five  ex- 
perimental balls  of  it,  not  exceeding  an  inch  in  diameter.  Allow 
them  to  set  with  warmth,  and  cool  again,  which,  in  good  but  rather 
slow-setting  cement,  will  require  about  half  an  hour ;  after  which  put 
two  or  three  of  them  into  a  basin  of  water.  If  they  continue  to  set 
m  this  state,  and  become  very  hard  in  the  course  of  a  day  or  two, 
the  cement  is  good;  but  if  on  the  contrary  they  do  not  become  very 
hard  in  this  time,  both  inside  and  out,  whether  previously  kept  in  air 
or  water,  the  cement  is  not  in  a  fit  state  to  be  used,  and  should  Do 
rejected. 

2ndly.  Rule  for  ascertaining  whether  cement  of  improper  quality 
has  originally  been  good,  but  injured  by  becoming  stale,  or  whether 
it  may  not  have  been  either  the  produce  of  bad  cement  stone,  or  of 
good  cement  stone  adulterated  after  calcination,  which  two  last  cases 
cannot  be  discriminated  in  cement  prepared  for  sale: — 


QUALITIES  OF  CEMENT. 


161 


If  the  experimental  balls,  made  as  last  described,  will  not  set  pro- 
perly either  in  air  or  water,  the  next  point  is  to  ascertain  the  cause. 
For  this  purpose,  burn  the  same  balls  in  a  crucible  for  two  or  three 
hours  in  a  common  fire-place,  exposing  them  to  a  full  red  heat,  until 
they  ceased  to  effervesce  with  acids ;  then  pound  the  calcined  cement 
in  a  mortar  till  you  reduce  it  to  an  impalpable  powder,  and  mix  it  up 
once  more  into  experimental  balls  with  water.  If  the  cement,  after 
being  thus  re-burned,  should  set  well  both  in  air  and  under  water,  it 
is  a  proof  that  it  was  originally  good,  but  had  been  spoiled  by  exposure 
to  air  and  damp. 

If  on  the  contrary  the  cement  was  in  a  state  unfit  for  use,  should 
not  be  improved  by  the  above  process,  which  completely  restores  the 
virtue  not  only  of  stale  cement  if  originally  good,  but  also  of  stale 
lime,  it  is  a  proof  that  it  has  either  been  made  of  inferior  cement 
stone,  or  that  it  has  been  adulterated  by  mixing  earth  or  sand  of  the 
same  color,  with  the  cement  powder. 

3dly.  Kule  for  judging  of  the  comparative  cohesive  strength  of  dif- 
ferent sorts  of  cement : — 

Having  ascertained  that  the  cements  to  be  compared  together  are  in 
a  serviceable  state,  by  the  the  foregoing  rules,  without  which  further 
trouble  would  be  useless,  two  modes  present  themselves  for  judging  of 
their  comparative  strength ;  one,  the  usual  mode  of  setting  out 
bricks  from  a  wall  or  forming  a  suspensory  arch,  and  the 
other,  by  what  is  termed  the  breaking-down  apparatus,  consisting  of 
a  scale-board,  planks  and  weights,  and  a  couple  of  pairs  of  nippers  to 
be  used  with  a  gyn  or  triangle,  the  operation  of  which  we  will  now 
describe :  Provide  two  pieces  of  lay  stone,  or  any  other  sound  hard 
stone,  each  exactly  10  inches  long,  4  inches  broad,  and  4  inches  deep, 
more  or  less,  prepared  with  mortices  in  the  sides,  one  inch  wide  and 
one  inch  deep,  and  from  J  an  inch  to  i  high,  to  receive  the  nip- 
pers, which  should  be  so  placed  as  to  have  at  least  2  |  inches  of 
solid  stone  above  and  below  them  ;  the  abutting  surfaces  of  the  stone 
after  being  properly  squared  to  match,  should  be  jagged  or  roughed  to 


162 


QUALITIES  OF  CEMENT. 


the  depth  of  about  §th  of  an  inch,  or  indented  with  a  mason's  pick, 
Blight  or  ten  pairs  of  such  stones  should  be  prepared  for  each  sort  of 
cement  for  the  purpose  of  trying  several  experiments  at  the  same  time; 
these  stones  must  be  cemented  together  in  pairs,  with  the  different 
specimens  of  cement  laid  on  uniformally,  and  with  a  joint  not  exceed- 
ing one  quarter  of  an  inch  in  thickness,  and  then  allowed  to  remain 
10  or  12  days  to  properly  set  and  indurate  according  to  the  weather 
or  the  season  of  the  year.  These  are  to  be  suspended  to  a  beam,  or 
shears,  with  a  scale  or  plank  attached  below  to  receive  the  weights, 
with  which  it  is  to  be  loaded ;  then  apply  the  weights  equally  to  each 
specimen,  aud  carefully  note  down  each  transaction,  and  register  the 
breaking  weight  of  each  sample,  the  time  under  trial,  and  circum- 
stances and  nature  of  the  fracture.  The  comparisons  should  be  made 
separately,  with  the  quick  or  slow  setting  cements ;  otherwise  it  will 
be  unfair,  as  some  cements  are  as  fully  indurated  in  10  or  12  days,  as 
others  in  3  or  4  months. 

In  order  to  ascertain  more  precisely  the  effect  which  sand  produces 
on  the  cohesion  of  cement,  I  caused  three  little  brick  masses  to  be  con- 
nected by  pure  cement,  and  three  others  to  be  joined  by  a  mixture  of 
the  same  cement  with  clear  sharp  sand  in  equal  parts,  by  measure, 
and  in  order  to  compare  their  relative  cohesiveness  with  that  of  old 
chalk  lime  mortar  also,  I  caused  some  little  masses  to  be  cut  out  of 
the  best  brick  walls,  built  with  mortar  of  this  description,  which  I 
could  find  within  Chatham  lines ;  and  having  prepared  these  small 
specimens  with  proper  mortices  to  receive  the  nippers,  the  whole 
were  torn  asunder  in  the  usual  manner,  by  successive  weights,  as  stated 
below. 


163 


COMPARATIVE  COHESIVE  STRENGTH  OF  PURE  CEMENT,  OP  CEMENT 
MIXED  WITH  SAND,  AND  OF  COMMON  CHALK  LIME  MORTAR. 


No.  of 
Expt. 

Whether  with  cement  or 
chalk  lime  mortar. 

Age  in  daijs 
or  years. 

Weight  in  Ihs. 
which  broke  joint 

Average  breaking 
weight  in  lbs. 

1 

2 

o 

6 

■ 

■  Pure  cement. 

11  days. 
pZ  days. 

1241 
1003 
iUoi 

; 

•  1092 

1 

2 
3 

•  Cement  and  Sand. 

)  11  days. 
J  17  days. 

205 
257 
343 

.  225 

1 

2 

334 
64 

3 
4 

-  Chalk  lime  mortar 

-30  years. 

75 
47 

^  155 

5 
6 

205 
204 

Hence  it  appears  that  pure  cement  is  more  than  four  times  as 
strong  at  the  same  age,  as  the  customary  mixture  of  cement  and  sand 
in  equal  parts,  as  in  common  use.  Mr.  Brunei  was  therefore  quite 
right  in  employing  only  pure  cement  in  the  arches  of  the  Thames 
Tunnel  (England),  and  which  method  ought  to  be  adopted  in  all 
works  of  risk  or  importance.  Yet  in  all  works  of  less  importance, 
the  addition  of  an  equal  volume  of  sand  is  not  to  be  reprobated,  be- 
cause this  proportion,  whilst  it  renders  the  cement  mortar  cheaper,  is 
not  sufficient  to  take  away  its  hydraulic  properties,  and  even  when 
but  17  days  old,  it  appears  from  these  experiments  to  equal,  if  not  to 
exceed  the  strength  of  the  best  lime  mortar  of  30  years  of  age,  and  I 
conceived  it  probable,  that  if  tried  at  a  greater  age,  the  cement  mor- 
tar would  exceed  the  strength  of  the  chalk  lime  mortar,  in  a  five-fold 
rate. 

The  author  (Col.  Pasley)  next  describes  a  series  of  experiments 
which  he  made  of  the  comparative  adhesiveness  of  cement  to  bricks 
and  various  sorts  of  stone,  the  results  of  which  appear  as  follows ;  tho 


164      COMPAEATIVE  STRENGTH  OF  CEMENTS, 


period  of  the  trials  extended  from  the  latter  end  of  December,  1836, 
to  the  middle  of  May,  1837.  The  age  of  the  cement  was  in  general 
11  days,  in  two  instances  only  having  been  extended  to  12  days. 

The  first  12  experiments  were  with  bricks,  the  average  fracturing 
weight  was  1359  lbs. 

The  next  5  experiments  were  with  Bath  stone,  average  fractur- 
ing weight  1103  lbs. 

Then  followed  6  experiments  on  Cornish  granite,  which  separated 
with  an  average  weight  of  900  lbs. 

The  next  5  experiments  were  with  Portland  stone,  which  fractured 
with  an  average  of  856  lbs. 

Then  5  experiments  on  Yorkshire  landing  stones,  the  average  frac- 
turing weight  of  which  was  823  lbs. 

The  next  5  experiments  were  with  Kentish  rag-stone,  the  average 
breaking  weight  being  1349  lbs.  showing  the  adhesive  power  to  be 
nearly  equal  to  that  of  bricks. 

Then  followed  5  experiments  with  Craigleith  stone  (Scotch)  the 
average  breaking  weight  being  855  lbs. 

The  last  2  experiments  were  Vvdth  Cornish  granite  polished  on 
the  cementing  surfaces,  the  fracturing  weight  of  which  averaged 
928  lbs.,  which,  therefore,  nearly  equalled  in  strength  to  experi- 
ments Nos.  4  and  5  with  Cornish  granite  (rough)  which  averaged, 
1213  lbs. 

The  discrepancies  which  were  apparent  in  the  results  of  some  of 
the  foregoing  experiments,  were  considered  to  be  owing  to  the  con- 
dition of  the  cement,  some  of  which  were,  at  the  time  of  using,  more 
fluid  than  others.  Upon  the  whole,  these  experiments  are  not  fully 
conclusive,  but  we  safely  infer  from  them  that  the  adhesiveness  of 
cement  to  the  least  congenial  sort  of  stone  is  more  than  one  half,  and 
nearly  two-thirds  of  its  adhesiveness  to  bricks,  and  that  it  appears  to 
adhere  to  hard  stones  with  a  greater  tenacity  than  to  soft  ones,  and 
also  that  the  state  of  the  surfaces  operated  upon,  whether  more  or 
less  smooth  is  of  very  little  importance,  but  these  experiments  fully 


COMPARATIVE  STRENGTH  OF  CEMENTS.  165 


prove  that  pure  cement  attaches  itself  to  the  most  refractory  sort 
of  stone  with  five  times  as  much  adhesive  force  in  11  days,  as  the 
best  chalk  Ume  used  in  brickwork  is  capable  of  attaining  in  80 
years. 


ADDENDA. 


AMERICAN  RESOURCES. 

The  United  States  furnish  excellent  limestone,  principally  of 
primary  formation.  One  range  which  passes  unbroken  through  seve- 
ral of  the  States  is  perhaps  one  of  the  most  extensive  and  valuable 
primary  limestones  in  the  world. 

(Extract  from  Mahan's  Engineering.)  Limestone  is  so  extensively 
diffused  throughout  the  United  States,  and  is  quarried,  either  for 
building  stone  or  to  furnish  lime,  in  so  many  localities,  that  it  would 
be  impracticable  to  enumerate  all  within  any  moderate  compass.  One 
of  the  most  remarkable  formations  of  this  stone  extends,  in  an  unin- 
terrupted bed,  from  Canada,  through  the  States  of  Vermont,  Massa- 
chussets,  Connecticut,  New  York,  New  Jersey  and  Virginia,  and  in 
all  probability,  much  further  south. 

Limestone  is  burned  in  almost  every  locality  where  deposits  of  the 
stone  occur.  Thomaston,  in  Maine,  has  supplied,  for  some  years,  most 
of  the  markets  on  the  seaboard  with  a  material  which  is  considered  as 
a  superior  article  for  ordinary  building  purposes.  One  of  the  greatest 
additions  to  the  building  resources  of  our  country  was  made  in  the 
discovery  of  the  hydraulic  or  water  limestone  of  New  York.  The  pre- 
paration of  this  material,  so  indispensable  for  all  hydraulic  works  and 
heavy  structures  of  stone,  is  carried  on  extensively  at  Rondout,  on  the 
Delaware  and  Hudson  canal  in  Madison  county,  and  is  sent  to  every 
part  of  the  United  States,  being  in  great  demand  for  all  the  public 
works  carried  on  under  the  superintendence  of  our  civil  and  military 
engineers. 

A  not  less  valuable  addition  to  our  building  materials  has  been 


AMERICAN  RESOURCES. 


167 


made  by  Prof.  W.  B.  Rogers,  who,  a  few  years  since  directed  the  at- 
tention of  engineers  to  the  dolomites,  for  their  good  hydraulic  proper- 
ties. From  experiments  made  by  Vicat,  in  France,  who  first  there 
observed  the  same  properties  in  the  dolomite,  and  from  those  in  our 
own  country,  it  appears  highly  probable  that  the  magnesian  lime- 
stones, containing  a  certain  proportion  of  magnesia,  will  be  found 
fully  equal  to  the  argillaceous,  from  which  hydraulic  lime  has  hitherto 
been  solely  obtained. 

(Extract  from  Prof.  Daniel's  Lecture,  before  the  Chicago  Academy 
of  Natural  Science.)  A  magnesian  limestone  which  forms  the  heights 
of  the  Upper  Mississippi,  extends  south-west  across  the  Wisconsin 
River,  and  westward  into  Minnesota.  At  Lasalle,  Illinois,  it  fur- 
nishes an  excellent  hydraulic  cement. 

The  Trenton  limestone,  70  feet  thick,  is  a  hard,  thin-bedded  blue 
limestone,  often  wholly  made  up  of  shells  and  corals,  above  this  is  the 
Galena  limestone,  250  feet  thick.  Then  comes  the  Hudson  River  rocks, 
in  whose  lower  portion  are  found  shell  beds  as  rich  as  those  of  the 
Trenton  limestone,  bnt  of  different  species.  They  form  the  base  of 
the  mounds  around  Galena  and  through  the  lead  region. 

Joliet,  the  city  of  stone  quarries,  lies  in  the  old  river  bed  of  the  once 
mighty  Des  Plaines,  now  reduced  to  a  small  stream.  East  and  west 
are  rocky  bluffs.  The  valuable  and  inexhaustable  quarries  extend 
more  than  20  miles  north  and  south,  and  near  the  upper  end  is  the 
little  town  of  Athens,  which  gives  its  name  to  the  celebrated  store 
used  in  Chicago.  Five  miles  from  Joliet  is  Lockport,  underlaid  by 
quarries,  for  who  has  not  heard  of  the  Lockport  stone  ?  Athens  comes 
next,  and  here  Joliet  has  a  competitor.  The  stone  is  of  better  quality, 
and  more  easily  obtained.  Athens  is  simply  a  vast  stone  quarry,  and 
wiU  never  be  anything  else. 

(Extract  from  Mahan's  Engineering.)  Lime  considered  as  a 
building  material,  is  now  usually  divided  into  three  principal  classes, 
common  or  air  lime,  hydraulic  lime,  and  hydraulic  or  water  ce- 
ment. 


168 


ANALYSIS  OF  CEMENTS. 


The  Kmestones  which  yield  hydraulic  limes  and  cements  are  either 
argillaceous,  or  magnesian,  or  argilo-magnesian.  The  products  of 
their  calcination  vary  considerably  in  their  hydraulic  properties. 
Some  of  the  hydraulic  limes  harden,  or  set  very  slowly  under  water, 
while  others  set  rapidly.  The  hydraulic  cements  set  in  a  very  short 
time.  This  diversity  in  the  hydraulic  energy  of  the  argillaceous  lime- 
stones arises  from  the  variable  proportions  in  which  the  lime  and  clay 
enter  into  their  composition. 

M.  Petot,  in  an  able  work  entitled,  "Kecherches  sur  la  ChaufFour- 
nerie,"  gives  the  following  table,  exhibiting  those  combinations,  and 
the  results  obtained  from  their  calcination : — 


Idme 

Clay, 

RemUing  products. 

100 

0 

Very  fat  lime. 

90 

10 

Lime,  a  little  hydraulic. 

80 

20 

Do.   quite  hvdraulic. 

70 

30 

Do.  'do. 

60 

40 

Plastic  or  hydraulic  ce- 

ment. 

50 

50 

Do.  do. 

40 

60 

Do.  do. 

30 

70 

Calcareous  puzzolana, 

(brick). 

20 

80 

Do.          do.  do. 

10 

90 

Do.          do.  do. 

0 

100 

Puzzolana  of  pure  clay  do. 

Distinctive  cha/racters  of  the  products. 


Incapable  of  hardening  in  water. 
)  Slakes  like  pure  lime,  when  pro- 

V  perly  calcined,  and  hardens 
)     under  water. 

)  Does  not  slake  under  any  cir- 
>.  cumstances,  and  hardens  nn- 
)     der  water  with  rapidity. 

)  Does  not  slake  nor  harden  un- 

V  der  water,  unless  mixed  with 
)     a  fat  or  a  hydraulic  lime. 
Same  as  the  preceding. 

The  most  celebrated  European  hydraulic  cements  are  obtained  from 
argillaceous  limestones,  which  vary  but  slightly  in  their  constituent 
elements  and  properties.  The  following  table  gives  the  results  of 
analysis  to  determine  the  relative  proportions  of  lime  and  clay  in  these 
cements : — 

LOCALITY.  LIME.  CLAY. 

English  (commonly  known  as  Parker's,  or  Roman  ce- 
ment),  5540  44-60 

French  (made  from  Bologne  pebbles),   54-00  46*00 

Do.    (Pouilly),   42-86  57-14 

Do.        do   36-37  63-63 


ANALYSIS  OF  CEME^JTS. 


169 


LOCALITY. 


LIMB.  CLAY. 


French  (Baye), 
Russian,  


21-62  78-38 


62^00  38-00 


The  best  known  hydraulic  cements  of  the  United  States  are  manu- 
factured in  the  State  of  New  York ;  the  following  analyses  of  some  of 
the  hydraulic  limestones,  from  the  most  noted  localities,  published  in 
the  Geological  Report  of  the  State  of  New  York,  1839,  are  given  by 
Dr.  Beck. 

ANALYSIS  OF  THE  MANLIUS  HYDRAULIC  LIMESTONE 

Carbonic  acid,   .....o.. ,..39-80 

Lime,  2624 

Magnesia,  18-80 

Silica  and  alumina,  13  -50 

Oxide  of  iron,   1  -25 

Moisture  and  loss,   1-41 


This  stone  belongs  to  the  same  bed  which  yields  the  hydraulic  ce- 
ment obtained  near  Kingston,  in  Upper  Canada. 

ANALYSIS  OF  THE  CHITTENANGO  HYDRAULIC  LIMESTONE  BEFORE 
AND  AFTER  CALCINATION. 


100-00 


TTNBUENT. 


Carbonic  acid, 


39-33    Carbonic  acid  and  moisture  10-90 


Lime, 


25-00  Lime, 


39-50 


Magnesia, 
Silica,  


17-83  Magnesia,   22-27 

11-76  Silica,   16.56 

2*73  Alumina  and  oxide  of  iron,  10*77 

1-50 


Alumina,  

Peroxide  of  iron, 
Moisture,  


1-85 


10000 


100-00 


8 


170 


ANALYSIS  OF  CEMENTS. 


ANALYSIS  OF  THE  HYDRAULIC  LIMESTONE  FEOM  ULSTEB  COUNTT, 
ALONG  THE  LINE  OP  THE  DELAWABB  AND  HUDSON  CANAL, 
BEFOEE  AND  AFTER  BURNING. 

XTNBUENT.  BUENT, 


Carbonic  acid,   34-20  5-00 

Lime,   25*50  37-60 

Magnesia,   12-35  16-65 

Silica,   15-37  22  75 

Alumina,   9-13  13-40 

Oxide  of  iron,   2-25  3-30 

Bituminous  matter,  moisture  and  loss,   1-20  1-30 


100-00  100-00 

The  hydraulic  properties  of  the  magnesian  limestones  of  the  United 
States  were  noticed  by  Prof.  W.  B.  Rogers,  who,  in  his  Report  of  the 
Geological  Survey  of  Virginia,  1838,  has  given  the  following  analysis 
of  some  of  the  stones  from  different  localities  : — 


No.  1. 

No.  2. 

No.  3. 

No.  4. 

  55-80 

53-23 

48-20 

55  03 

41-00 

35-76 

24-16 

...  1-50 

0-80 

1-30 

2-60 

2-50 

2-80 

12-10 

15-30 

0-40 

2-73 

1-20 

  0-60 

1-77 

0-01 

1-71 

100-00 

100  00 

100-00 

100-00 

The  limestone  No.  1  of  the  above  table  is  from  Sheppardstown  on  the 
Potomac,  in  Virginia,  it  is  extensively  manufactured  for  hydraulic 
cement.  No.  2  is  from  the  Natural  Bridge,  and  banks  of  Cedar 
Creek,  Virginia ;  it  makes  a  good  hydraulic  cement.  No.  3  is  from 
New  York,  and  is  extensively  burned  for  cement.  No.  4  is  from 
Louisville,  Kentucky,  said  to  make  a  good  cement. 

M.  Vicat  states  that  a  magnesian  limestone  of  France  containing 
the  following  constituents,  lime  40  parts,  magnesia  21,  and  silica  21, 


ANALYSIS  OF  CEMENTS. 


171 


yields  a  good  hydraulic  cement,  and  he  gives  the  following  analysis  of 
a  stone  which  gives  a  good  hydraulic  lime : — 


Carbonate  of  lime,  50*60 

Carbonate  of  magnesia,  42*00 

Silica,   5*00 

Alumina,  ,   2*00 

Oxide  of  iron,   0*40 


10000 

Experiments  by  several  eminent  chemists  have  extended  the  list  of 
natural  substances  which,  when  properly  burnt  and  reduced  to  powder, 
have  the  same  properties  as  Puzzolana.  They  mostly  belong  to  the 
feldspathic  and  schistoze  rocks,  and  are  either  fine  sand  or  clays  more 
or  less  indurated. 

The  following  table  gives  the  results  of  analyses  of  Puzzolana,  trass, 
a  basalt,  and  a  schistus,  which,  when  burnt  and  powdered,  were  found 


to  possess  the  properties  of  Puzzolana : — 

PUZZOLANA, 

TRASS. 

BASALT. 

BOHISTTTS. 

0-570 

44*50 

46-00 

0*120 

16*75 

26*00 

0-026 

9-50 

4*00 

  0*047 

0-010 

  0*120 

0*050 

20-00 

14*00 

2  37 

8*00 

  0*014 

0-070 

  0*030 

0*010 

2*60 

  0*106 

0-144 

4*28 

2*00 

1*000 

1-000 

100*00 

100*00 

All  of  these  substances,  when  prepared  artificially,  are  now  general- 
ly known  by  the  name  of  artificial  Puzzolanas,  in  contradistinction  to 
those  which  occur  naturally. 

(Extracts  from  Mr.  Kirwan.)  Puzzolana,  reddish  or  reddish-brown, 
gray,  or  grayish-black : — That  of  Naples  is  generally  gray,  that  of 
Civita  Vecchia  more  generally  reddish,  or  reddish-brown. 


172 


ANALYSIS  OF  CEMENTS. 


Its  surface,  rongh,  uneven,  and  of  a  baked  appearance.    It  comes 
to  us  in  pieces  of  from  the  size  of  a  nut  to  that  of  an  egg. 
Its  internal  lustre,  0.    Its  transparency,  0. 

Its  fracture  uneven,  or  earthy,  and  porous,  commonly  filled  with 
particles  of  pumice,  quartz,  scorise,  &c. 

Hardness,  3 ;  very  brittle ;  specific  gravity,  from  2.570,  which  is 
that  of  the  black,  to  2.785,  rarely  2.8 ;  has  an  earthy  smell. 

It  is  not  diffusible  in  cold  water,  but  in  boiling  water  it  gradually 
deposits  a  fine  earth.    It  does  not  effervesce  with  acids. 

Heated,  it  assumes  a  darker  color,  and  easily  melts  into  a  bla-ck 
slag,  or  with  borax  into  a  yellowish  green  glass. 

It  is  magnetic  before  it  is  heated,  but  not  after ;  this  is  the  most  re- 
markable of  its  properties. 

By  Mr.  Bergman's  analysis,  it  contains  from  55  to  60  per  cent,  of 
silex,  19  to  20  of  argill,  and  from  15  to  20  of  iron. 

When  mixed  with  a  small  proportion  of  lime  it  quickly  hardens, 
and  this  induration  takes  place  even  under  water.  This  singular  prop- 
erty appears  to  me  to  proceed  from  the  magnetic  state  of  the  iron  it 
contains,  for  this  iron  being  unoxygenated,  subtilely  divided,  and  dis- 
persed through  the  whole  mass,  and  thus  offering  a  large  surface, 
quickly  decomposes  the  water  with  which  it  is  mixed,  when  made  into 
mortar,  and  forms  a  hard  substance  analogous  to  the  specular  iron 
ore  as  it  does  in  the  iron  tubes  in  which  water  is  decomposed  in  Mr, 
Lavoiser's  and  Dr.  Priestley's  experiments;  for  in  these  the  iron 
swells  and  increases  in  bulk,  and  so  does  Puzzolana  when  formed  into 
mortar.  One  principal  use  of  lime  seems  to  be  to  heat  the  water,  as 
while  cold  it  cannot  readily  pervade  the  caked  argill  that  invests  the 
ferruginous  particles,  yet  in  time  even  cold  water  may  pervade  it,  and 
produce  hardness,  and  hence  lavas  become  harder  when  moistened,  as 
Mr.  Dolomieu  has  observed.  If  the  mortar  be  long  exposed  to  the 
atmosphere,  fixed  air,  as  well  as  pure  air,  will  unite  to  the  iron,  rust 
will  be  produced,  and  the  mortar  will  not  then  harden,  as  Dr.  Hig- 
gins  has  also  noticed.    Clay  over  which  lava  has  flowed  is  frequently 


ANALYSIS  OF  CEMENTS.  173 

converted  into  Puzzolana.  But  volcanic  scoriae  never  afford  it,  either 
because  they  are  much  calcined,  or  retain  sulphur,  or  its  acid. 

Trass  or  terras.  I  couple  this  with  Puzzolana  on  account  of  their 
similarity  to  each  other,  and  not  because  I  look  upon  it  as  constantly 
and  necessarily,  a  volcanic  production.  On  the  contrary,  I  believe  it 
to  be  generally  the  product  of  pseudo-volcanoes  or  external  fires.  It 
is  found  in  many  places,  but  principally  near  Andernach,  in  the  vi- 
cinity of  the  Khine,  also  near  Frankfort,  Cologne,  Pleith,  &c.,  and 
there  called  tuff  stein.  It  is  found  in  valleys  some  feet  under  the  sur- 
face, to  which  no  stream  of  water  has  had  access  ;  sometimes  in 
columnar  masses  of  a  gray  or  Isabella  yellow  color,  some  round  and 
some  quadrangular,  standing  close  to  each  other,  and  forming  inter- 
nally one  common  mass.  According  to  Mr.  Bergman,  it  consists  of 
nearly  the  same  principles  as  Puzzolana,  only  the  calcareous  seems 
more  plentiful  in  this.  Artificial  terras  or  Puzzolana  is  made  by 
burning  clays  or  slates  that  abound  in  iron,  and  then  grinding  them 
to  a  fine  powder. 

Tufas.  These  seem  to  be  a  Puzzolana  formed  by  nature  into  a 
mortar. 

Piperino.  This  also  seems  a  concretion  of  volcanic  ashes,  and  is 
said  to  be  the  substance  that  covers  Pompeia.  It  seems  to  differ  from 
tufas,  in  containing  more  heterogenities,  being  in  fact  a  kind  of  por- 
phyiy,  or  breccia,  and  being  more  easily  decomposed  by  exposure  to 
moisture  and  the  open  air,  but  if  preserved  from  moisture,  it  hardens 
when  exposed  to  the  air. 

Cement.  In  1770  M.  Loriet  pretended  to  have  discovered  the  se- 
cret of  the  cement  of  the  ancient  Romans,  which,  according  to  him, 
was  only  a  mixture  of  powdered  quick-lime  with  lime  which  had  been 
long  slaked  and  kept  under  water.  The  slaked  lime  was  first  to  be 
made  up  with  sand,  earth,  brick-dust  &c.,  into  mortar,  and  then  about 
one-third  of  quick-lime  in  powder  added  to  the  mixture.  This  pro- 
duced an  almost  instantaneous  petrifaction,  something  like  what  is 
called  the  setting  of  alabaster.    But  the  invention  of  this  cement  has 


174 


STRENGTH  OF  MORTAR. 


not  succeeded  to  the  degree  the  inventor  expected,  owing  to  the  pre- 
cision necessary  in  its  preparation.  Dr.  Black  informs  us  that  a  ce- 
ment of  this  kind  is  certainly  practicable.  It  is  done,  he  says,  by 
powdering  the  lime  while  hot  from  the  kiln,  and  throwing  it  into  a 
thin  paste  of  sand  and  water,  which,  not  slaking  immediately,  absorbs 
the  water  from  the  mortar  by  degrees,  and  forms  a  very  hard  mass. 
It  is  plain,  he  adds,  that  the  strength  of  this  mortar  depends  on  using 
the  lime  hot  or  fresh  from  the  kiln. 

STRENGTH  OP  MORTABS, 

A  very  wide  range  of  experiments  has  beeii  tnade,  by  engineers 
both  at  home  and  abroad,  upon  the  resistance  offered  by  mortars  to 
a  transversal  strain,  with  a  view  to  compare  their  qualities.  As 
might  naturally  have  been  anticipated,  these  experiments  have  pre- 
sented very  diversified,  and,  in  many  instances,  contradictory  results. 

M.  Vicat  gives  the  following  as  the  average  resistance  on  the 
square  inch  offered  by  mortars  to  a  force  of  tractioo,  the  deductions 
being  drawn  from  experiments  on  the  resistance  to  a  transversal 


strain : — 

Mortars  of  very  strong  hydraulic  lime,  170  pounds. 

ordinary  "  140 

medium  "   100 

common  lime,  ,   40  " 

"  "  (bad  quality)   10  " 


These  experiments  were  made  upon  prisms  a  year  old,  which  had 
been  exposed  to  the  ordinary  changes  of  weather. 

General  Treussart,  in  his  work  on  hydraulic  and  common  mortars, 
has  given  in  detail,  a  large  number  of  experiments  on  the  transversal 
strength  of  artificial  hydraulic  mortars,  made  by  submitting  rectan- 
gular parallelopipeds  of  mortar,  6  inches  in  length  and  2  inches 
square,  to  a  transversal  strain  applied  at  the  centre  point  between 
bearings  4  inches  apart.  From  these  he  deduces  the  following  prac 
tical  conclusions : — 


STRENGTH  OF  CONCRETE 


175 


That  when  the  parallelepipeds  sustain  a  transversal  strain  varying 
between  220  and  330  lbs.  the  corresponding  mortar  will  be  suitable 
for  common  gross  masonry,  but  that  for  important  hydraulic  works 
the  parallelopipeds  should  sustain  before  yielding,  from  330  to  440  lbs. 

The  only  published  experiments  on  this  subject  made  in  this  country 
are  those  of  Colonel  Totter,  appended  to  his  translation  of  General 
Treussart's  work. 

From  experiments,  Colonel  Totten  deduces  the  following  general 
results : — 

1st.  That  mortar  of  hydraulic  cement  and  sand  is  the  stronger  and 
harder  as  the  quantity  of  sand  is  less. 

2d.  That  common  mortar  is  the  stronger  and  harder  as  the  quan- 
tity of  sand  is  less. 

3d.  That  any  addition  of  common  lime  to  a  mortar  of  hydraulic 
cement  and  sand  weakens  the  mortar,  but  that  a  little  lime  may  be 
added  without  any  considerable  diminution  of  the  strength  of  the 
mortar,  and  with  a  saving  of  expense. 

4th.  The  strength  of  common  mortars  is  considerably  improved  by 
the  addition  of  an  artificial  Puzzolana,  but  more  so  by  the  addition  of 
an  hydraulic  cement. 

5th.  Fine  sand  generally  gives  a  stronger  mortar  than  coarse  sand. 

6th.  Lime  slaked  by  sprinkling  gave  better  results  than  lime  slaked 
by  drowning.  A  few  experiments  made  on  air-slaked  lime  were  un- 
favorable to  that  mode  of  slaking. 

7th.  Both  hydraulic  and  common  mortar  yielded  better  results 
when  made  with  a  small  quantity  of  water  than  when  made  thin. 

8th.  Mortar  made  in  the  mortar-mill  was  found  to  be  superior  to 
that  mixed  in  the  usual  way  with  a  hoe. 

9th.  Fresh  water  gave  better  results  than  salt  water. 

STRENGTH  OF  CONCRETE  AND  BETON. 

From  experiments  made  on  concrete,  prepared  according  to  tho 
most  approved  process  in  England,  by  Colonel  Pasley,  it  appears  that 


176  STRENGTH  OF  CONCKETE. 

that  this  material  is  very  inferior  in  strength  to  good  brick  and  the 

weaker  kinds  of  natural  stones. 

Concrete. — This  term  is  applied  by  English  architects  and  en- 
gineers, to  a  mortar  of  finely  pulverized  quick-lime,  sand  and  gravel. 

Beton. — The  term  beton  is  applied  by  French  engineers  to  any 
mixture  of  hydraulic  mortar  with  fragments  of  brick,  stone,  or  gravel, 
and  it  is  now  also  used  by  English  engineers  in  the  same  sense. 

From  experiments  made  by  Colonel  Totten  on  beton,  the  following 
conclusions  are  drawn  : — 

That  beton  made  of  a  mortar  composed  of  hydraulic  cement,  com- 
mon lime,  and  sand,  or  of  a  mortar  of  hydraulic  cement  and  sand, 
without  lime,  was  the  stronger  as  the  quantity  of  sand  was  the  smaller, 
But  there  may  be  0*50  of  sand,  0-25  of  common  lime,  without  sensi- 
ble deterioration,  and  as  much  as  1*00  of  sand,  and  0*25  of  lime. 
^7ithout  great  loss  of  strength. 

Beton  made  with  just  sufficient  mortar  to  fill  the  void  spaces  between 
the  fragments  of  stone  was  found  to  be  less  strong  than  that  made 
with  double  this  bulk  of  mortar.  But  Colonel  Totten  remarks, 
that  this  result  is  perhaps  attributable  to  the  difficulty  of  causing  so 
small  a  quantity  of  mortar  to  penetrate  the  voids,  and  unite  all  the 
fragments  perfectly,  in  experiments  made  on  a  small  scale. 

The  strongest  beton  was  obtained  by  using  quite  small  fragments 
of  brick,  and  the  weakest  from  small,  rounded,  stone  gravel. 

A  beton  formed  by  pouring  grout  among  fragments  of  stone  or 
brick,  was  inferior  in  strength  to  that  made  m  the  usual  way  with 
mortar. 

Comparing  the  strength  of  the  betons  on  which  the  experiments 
were  made,  which  were  eight  months  old  when  tried,  with  that  of  a 
sample  of  sound  red  sandstone  of  good  quality,"  it  appears  that  the 
strongest  prisms  of  beton  were  only  half  as  strong  as  the  sandstone. 

Previous  to  giving  my  experiments  and  by  way  of  conclusion  I  will 
just  remark  that,  in  making  computations  it  will  be  quite  safe  to  esti- 
mate a  cubic  foot  of  mortar  at  108  to  110  lbs.    Tenacity  50  lbs.  to 


VARIOUS  EXPERIMENTS. 


177 


the  square  inch,  and  specific  gravity  1*75;  sand  at  90  to  120  lbs.  j 
unslaked  lime  53  to  90  lbs.  ;  brick-dust  and  brick-work  at  112  lbs., 
and  limestone  at  171  to  197  lbs.  Mr.  Kirwan  gives. the  weight  of  a 
cubic  foot  of  Puzzolana  at  169-37  lbs.  and  specific  gravity  2-67. 


THE  FOLLOWING  ARE  THE  RESULTS  OF  VARIOUS 
EXPERIMENTS. 

No.  1.  A.  Stearns  &  Co.,  Bridgeport  Kiln,  Prairie  Stone. 

Thirty-three  cubic  inches  of  unslaked  lime  weighed  23  ounces,  gave, 
as  a  result  after  being  slaked  by  sprinkling,  a  volume  of  82.5  cubic 
inches  and  weighed  28.5  ounces,  equal  to  2.5  of  slaked  lime  to  1  of 
unslaked. 

No.  1. 

33.0  cubic  in.  fine  sand  27    ozs.  C    Mixed  as  mor- 

16.5  Utiea  hydraulic  cement   8  tar,  and  when  per- 

16.5  slaked  lime  5.7   "     fectly  dried  meas- 

    ured  48  cubic  ins. 

66.0  iO.7         Land  weigh'd  45  oz. 


No.  2. 


33.00  cubic  in.  sand  • 
8.25  Utica  cement 

8.25  slaked  lime 

49.50 


27.00  ozs.  f  Mixed  as  mor- 
4.00*'  tar,  and  when  per- 
2.85  "  'I  fectly  dried  meas- 

— - —        ured  34  cubic  ins. 

33.85       Land  weigh'd38  oz. 


No.  3. 


16.50  cubic  in.  slaked  lime 
5.50       *'  brick-dust 
11.00  sand 

33.00 


5.70  ozs.  r  Mixed  as  mor- 
5.59"  tar,  and  when  per- 
9.00  "    -{  fectly  dried  meas- 

 ur'd23.20cub'cin. 

20.29     Land  weigh'd  20  oz. 


VARIOUS  EXPERIMENTa 


No.  4. 


16.50  cubic  in.  Utica  cement, 


16.50  cubic 
16.50  " 
16.50  " 
8.25  " 


in.  sand 

pounded  brick 
Utica  cement 
slaked  lime 


57.75 


8.00  02S. 


No.  5. 


13.50  ozs. 
16.77  *' 

8.00 

2.85  " 


41.12 


Mixed  as  above, 
and  when  perfect 
ly  dried  measured 
16  cubic  ins.  and 
^weighed  11.50  oz. 


"  Mixed  as  above, 
and  when  per- 
fectly dried  meas- 
ured 45  cubic  ins. 
and  weighed  39 

.ozs, 


No.  6. 


16.50  cubic  in.  slaked  lime 


No.  7. 


8.25  cubic 
8.25 

16.50 


in.  slaked  lime 
Utica  cement 


5.7  ozs.^ 


2.85  ozs. 
4.00 

6.85 


Mixed  as  lime 
putty,  when  per- 
fectly dried,  meas- 
ur'dl2.75cub'cin. 
^and  weigh'd  7  oz. 

Mixed  as  above, 
and  when  perfect- 
ly dried  measured 
13.57  cubics  ins. 
^and  weighed  10  oz. 


No.  2.  B.   Stearns  &  Co.,  Bridgeport  Kiln,  Pbairie  Stone. 
58  cubic  inches  of  unslaked  lime  weighed  48*50  ozs.,  gave,  as  a  re- 
sult after  being  slaked  by  sprinkling,  a  volume  of  206*25  cubic  inches 
of  slaked  lime  and  weighed  57  ounces,  equal  to  3*55  of  slaked  lime  to 
1  of  unslaked. 

No.  8. 


203*00  cubic  inches  of  sand,  166*70  ozs. 

103*12  slaked  lime,  28*50  ** 

306-12  195*20 


Mixed  as  mortar 
as  7  of  sand  to  1 04 
unslaked  lime,  and 
when  thoroughly 
dried  measured 
201*13  cubic  ins, 
and  weighed  208 
L  ounces. 


VARIOUS  EXPERIMENTS. 


179 


No.  9. 


103-12  cubic  ins.  slaked  lime, 


Mixed  as  lim 
putty  and  pressed 
into  a  mould  and 
when  thoroughly 
28*50  ozs.  -{  dried  measured  54* 
60  cubic  inches  and 
weighed  30  ounces. 
This  contracted  in 
_  dry 'g  4-65  cubic  ins. 


'No,  3.  C.  Sheriman  &  Co.,  Lyons  Kiln,  Prairie  Stone. 
8*90  cubic  inches  of  unslaked  lime  weighed  7*5  ounces,  gave,  as  a 
result  after  being  slaked  by  sprinkling,  a  volume  of  23*29  cubic  inches 
of  slaked  lime,  and  weighed  9  ounces,  equal  to  2*62  of  slaked  lime  to 
1  of  unslaked. 

No.  10. 

Mixed  as  lime 
putty  and  pressed 
into  a  mould  and 
when  thoroughly 
9  ozs.  -l  dried  measured  1 5. 
85  cubic  inches  and 
weighed  9  -5  ozs. 
This  contracted  in 
^dry'g  1*67 cubic  in. 


23*29  cubic  inches  slaked  lime, 


No.  4.  D.  Sturtevant  &  Co.,  Kiln  near  Lyons,  Prairie  Stone. 

16*80  cubic  inches  of  unslaked  lime  weighed  14  ounces,  gave  as  a 
result  after  being  slaked  by  drowning,  a  volume  of  55  cubic  inches  oi 
slaked  lime,  and  weighed  17  ounces,  equal  to  3*33  of  slaked  lime  to 
1  of  unslaked. 

No.  11. 

r 


82*5  cubic  inches  of  fine  and  coarse 

sand,  67*50  ozs. 

55-0     «         "      slaked  lime,  17*00 


137.5 


S4-50 


Mixed  as  mortar 
as  1  1-2  of  sand  to 
1  of  slaked  lime  or 
as  5  of  sand  to  1  ot 
'{unslaked  lime, 

I nearly,  and  when 
P'i.'fesjly  drj^fl  mea- 
sured '97'ci',biu  ins.; 
'  '  Lwoi^hsd  100  (M^.  ' 


180 


COMPARATIVE  RESULTS. 

Weight  of 

Ko.  Names  of  Materia\3.  1  cubic  ft.  in  Iba, 

1  2  measures  of  sand,  1  Utica  hydraulic  cement,  1  slaked 

lime  (mortar)  *   101.25 

2  2       "     sand,  ^  Utica  hydraulic  cement,  J  slaked  lime 

(mortar)   120.70 

3  s       *'     sand,  i  brick-dust,  1  slaked  lime  (mortar)   93.10 

4  1       **     Utica  cement  (without  sand)   75.27 

5  1  sand,  1  brick-dust,  1  cement,  J  slaked  lime 

(mortar)   93.60 

6  1       **     slaked  lime  as  putty  (1st  experiment)   63.57 

7  J  slaked  lime,  J  Utica  cement   79.58 

8  7       "     sand  to  1  of  unslaked  lime  (mortar)   112.22 

9  1       "     slaked  lime  as  putty  (2d  experiment)...-   65.59 

10  1  "       "  (3d  )   64.08 

11  H  sand,  1  of  slaked  lime  (mortar)   111.33 

12  1       "     Utica  cement  exposed  to  the  air  5  months  be- 

fore being  mixed,  and  then  dried  for  3 
months   96.77 

13  1       "     Sandusky  cement,  fresh  from  cask  (without 

sand)   85.71 

14  1  measure  Utica  cement  1  1-2  of  sand,  under  water  for  117.02 

12  months,  and  then  dried  for  3  months 

15  1       "     Utica  cement,  2  of  sand,   121*93 

16  1       "     Utica  cement,  1  of  sand,   114-54 

17  1  sand,  1  slaked  lime  (mortar)   102-12 

18  Utica  hydraulic  cement,  in  a  dry  state  (in  cask)   52-36 

19  Unslaked  lime,  in  a  dry  state  (1st  experiment,)   75*27 

20  "  (2d  )   90*31 

21  (3d  )   91*01 

22  "  (4th        "       )   90.00 

23  Slaked  lime,  "         (1st         "      )   37*30 

24  "  (2d  )   29-88 

25  "       "  (3d  u^:.„   41-72 

2a  "  (4tlf-'    '  '\    .    33*38 

27   !3r^ckdThst,'   I'   110*00 


181 


COMPARATIVE  RESULTS— ContiKued. 

Weight  of  1 

No,  Names  of  Materials.  cubic  ft.  in  Iba. 

28  Fine  sand,  in  a  dry  state,  (Lake  Michigan)   88*36 

29  larger  grains,  in  a  dry  state,  (Lake  Michigan)    94 '90 

30  Coarse  sand,  large  grain,  in  a  dry  state  (pit  sand)   124*36 

Note. — M.  Berthier  says  that  a  late  analysis  of  Parker's  Roman 
cement  shows  that  its  constituents  are  of  chalk  and  common  clay 
and  he  proposes  the  manufacture  of  a  similar  cement  by  the  mere  mis- 
ture  of  them  in  certain  proportions.  Thus  one  part  of  the  clay  and 
two  and  a  half  parts  of  the  chalk  set  almost  instantly,  and  may,  tliere- 
iove..  be  regarded  as  Roman  cement. 


FINIS. 


PLATE  I. 


Fig.  3.  Fig.  4. 


Fig.  1,  plan  (or  horizontal  section).  Fig.  2,  section  on  line  E — F. 
Fig.  3,  section  on  shed,  and  part  of  exterior.  Fig.  4,  section  from  A 
towards  the  shed. 

A  Hatchway.  B  Furnace.  C  Grate-bars.  D  Ash-pit.  E  Rough 
chalk-ashes.  F  Level  of  ground  beneath  shed.  G  Level  of  ground 
at  hatchway. 


PLATE  n. 


CEMENT  KILN. 


PLATE  in. 


INDEX. 


PAGE. 


Acidulous  gas  in  the  induration  of  mortar,  agency  of.   46 

"            from  lime,  necessity  of  expelling..-   82 

Air  in  the  preparation  of  lime,  agency  of.   10 

Analysis  of  trass  and  puzzolana   113 

"        limestones,  and  mode  of  testing  their  several  properties  120 

Beton,  description  of  French   132 

Black  rock  of  Quebec   125 

Bricks,  observations  on..,   51 

Buildings,  cause  of  speedy  ruin  of,  and  precautions  necessary  to 

ensure  safety  of.   51 

effect  of  agitations  and  percussions  upon   " 

Caustic  or  quicklime,  on   55 

Cements  general  remarks  upon,  and  descriptions  of  varieties  of 

experiments  upon  old   52 

^'       specification  of  Dr.  Higgins'  patent   101 

water  on...   120 

"       Sheppy  and  Harwich  o-   122 

"      for  incrustations,  Dahl's,  Hamlin's,  Leardels,  mastic...  129 

*'      Beavan's  building  mortar   130 

"      for  floors,  terraces,  roofs,  &c.,  Venetian   " 

"      used  in  construction  of  Eddystone  lighthouse,  Smeaton's  131 

**      for  mending  earthenware,  cold  and  hot   135 

"      or  a'-tificial  puzzolana.  Frost's  water   " 

**      for  waterproof  purposes,  Dobb's   " 

"      for  floors,  &c.,  bituminous  limestone   137 

"  and  iron  rust,  plumbers'  and  coppersmiths'  diamond...  " 
"      for  manufacturing  purposes,  jewellers',  carpenters',  and 

sundry  other   138 

"      for  mouldings,  repairing  pipes  of  aqueducts,  air-pumps  " 

"      for  small  work,  for  marble  and  stone,  a  delicate   134 

Tartar   „ 

Parker's  Roman   133 

"      for  voltaic  plates  and  wooden  troughs,  chemists'  and 

statuaries,  steam,  electrical,  bituminous   139 


ii. 


INDEX. 


PAGE. 


Cement  for  uniting  stones,  floors,  &c.,  and  used  for  ironwork 

at  Southwark  Bridge,  London   140 

"        description  ot  kiln  for  burning  (with  illustration)   155 

"       rule  for  making  an  artifical   157 

"  "  "      equal  to  the  best  English 

water  cements   158 

"       rule  for  testing  the  qualities  of.   160 

"       comparative  cohesive  strength  of.   163 

properties  which  ought  to  be  fully  understood   124 

"       Thames  tunnel,  Lond.,  fully  establishes  the  character  of  ** 

"       experiments  on  artificial  (water)   126 

"       powder,  calcined   122 

Composition  for  mouldings  ,   134 

"         for  incrustations  132  and  135 

Experiments  showing  how  quickly  lime  imbibes  acidulous  gas 

and  is  injured  by  exposure  to  the  air   38 

**  showing  the  quantity  of  water  imbibed  by  lime...  40 

**  and  observations  made  to  determine  whether  mor- 
tar becomes  better  by  being  kept  long  before  it  is 

used   42 

**  showing  the  agency  of  acidulous  gas  in  the  in- 
duration of  mortar,  and  circumstances  which  im- 
pede or  promote  it   45 

showing  the  effects  of  finest  sand  and  quartoze 
powder  in  mortar;  observations  on  the  finest  cal- 
careous cements,  &c   67 

"         made  on  a  larger  scale,with  best  mixture  of  sands,&c,  67 

"         showing  the  integrant  parts  of  gravel   70 

"  "  effects  of  plaster-powder,  alum,  vi- 

triolic acid,  earth-salts,  and  alkalies  in  mortar,  &c.  73 
"         showing  the  eff'ects  of  skimmed  milk,  serum  of 
ox-blood,  decoction  of  linseed,  mucilage  of  linseed, 
linseed-oil  and  resin  in  mortar,  and  the  effect  of 

painting  incrustations   76 

showing  the  effect  ofsulphur  introduced  into  mortar  79 
"             "                   crude  antimony,  regulus  of 
antimony,  lead  matt,  potters'  ore,  white-lead,  &c., 
in  mortar   81 


INDEX.  iii. 

PAGE. 

Experiments  showing  the  effect  of  iron  scales,  colcothar,  ochres, 
&c.,  &c.,  in  mortar,  and  advice  concerning  inside 

stucco  and  damp  walls   83 

"         showing  the  effect  of  common  wood-ashes,  &c., 

&c.,  in  mortar   89 

**         showing  the  effect  of  bone  ashes  and  charred  bones, 
and  theory  of  their  agency  in  the  best  calcareous 

cements   95 

"         conclusions  drawn  from  other   127 

results  and  inferences  obtained  from   146 

Experimental  comparison  of  chalk  with  stone  lime ;  advice  to 
manufacturers  of  chalk-lime  concerning  the  art  of  making 

it  equal,  if  not  superior,  to  stone-lime   108 

Eelspar,  ground   132 

Eire-proof  floors,  on   146 

Elint-powder  injurious  to  mortar   64 

Gravel  in  mortar,  use  and  properties  of.   65 

"     a  substitute  for  sand,  varieties  of.   21 

"     remarks  on   65 

Gypsum,  and  other  earthy  matter  in  lime,  how  detected   9 

Hydrate  of  lime   58 

Hydraulic  lime,  M.  Berthiers   136 

**      mortar,  essential  constituents  of.   " 

"      limes,  M.Vicat's  method  of  preparing   145 

Incrustations  or  stuccoes,  experiments  or  remarks  on   67 

"         remark  on  method  of  coloring   83 

"         description  and  causes  of  damp  on,  and  remedies  for  86 

Kiln,  description  of  cement  (with  illustration)   155 

"   lime,  description  of  a  modern  (with  illustration)   150 

Lime  and  limestones,  remarks  on,  and  description  of  varieties  of  6 
"   Dr.  Higgins'  observations  and  experiments  on  the  different 

modes  of  burning  and  results   7 

"   the  art  of  making  good,  and  test  thereof.   10 

"   Dr.  Higgins' remarks  on  the  different  modes  of  slaking. . .  23 

"   injured  by  exposure  to  air   41 

"    qualifications  and  components  of  good   53 

"   effete  and  slaked   56 

<^  remarks  on  plasterers'   44 


iy.  INDEX. 

PAGE. 

Limes,  properties  of  rich,  meagre,  and  purest..**.   58 

"     observations  from  Lieut.-Col.  C.      Pasley's  work  on...  118 

"      on  water  or  hydraulic...   119 

"      expansion  of.   125 

"      M.  Vicat's  opinion  of  the  best  combinations  of.   144 

*'                    method  of  preparing  artificial  hydraulic   145 

"      on  the  measurement  of  -   148 

"      different  modes  of  measuring..............   149 

Limestone,  on  the  burning  of....,   150 

"        suited  for  hydraulic  cements,  varieties  of.   132 

*'        in  burning,  vitrification  of.   9 

Lime-water  in  the  composition  of  mortar,  superiority  of.   24 

Maltha,  on  the  ancient   133 

Manganese,  property  of  hardening  underwater   136 

Mortar,  components  of.  ........^   6 

*'     sundry^  ingredients  often  introduced  into   24 

on  the  composition  of  various  kinds  of ;  their  application, 
properties,  and  relative  values,  with  occasional  notes  of 

the  experiments  of  Dr.  Higgins  and. other  authorities...  25 

^     on.  the  induration  of.   30 

"     principal  cause  of  the  imperfection.of.......«   37 

**     on.  the  preparation  of  common   55 

*•     proper  consistency  and  induration  cf.   57 

"     relative  proportions  of  lime  and  sand  in   58 

on  various  substances  sometimes  added  to   59 

Plaster-of-Paris,  on   1 33 

Buzzolana,Col.Pasley's  inferences  from  various  experiments  upon  1 41 
"        M.  Vicat's  rules  for  judging  of  the  quality  of  natural 

or  artificial   142 

M.  Baggi,  Count  Chaptal,  Gen.  Treussart,  &c.,  ex- 
perience on  e   143 

**        description  of.   112 

"       analysis  of.   113 

"        artificial   114 

"        Col.  Pasley's  experiments  on  artificial   116 

Plasterers*  mortar,  remarks  upon   44 

Phlogisticated  air  in  chalk  and  limestone,  remarks  on   37 

ilecipes  for  coal-ash  mortar,  Dutch  terras  mortar,  and  puzzolana  141 


INDEX. 


V. 


PAOB. 


Recipes  various,  for  cements  and  mortars   129 

"     for  manufacturing  and  domestic  purposes   137 

Remarks-general   5 

Road-drift,  &c.,  varieties  and  qualifications,  and  test  of.   11 

Rubbish  in  mortar,  effect  of  old  ground   66 

Rubble,  Dr.Higgin's  experim'ts  on  sundry  varieties  of,  and  results  12 
"  **       in  the  composition  of  mortar.....  17 

"  ,  "    .   test  of  best  proportion  in  mortar   20 

Sand   10 

'  *  Dr.  Higgin's  remarks  on  varieties  used  for  building  purposes    1 2 

"  objectionable  for  mortar,  sea   10 

"  general  remarks  on  •  21 

"  remarks  on  washing  and  preparing   64 

"  and  lime,  sundry  experiments  and  results   33 

Trass  (Dutch),  or  terras,  description  of.   131 

"    analysis  of,  and  puzzolana   117 

Water,  description  of  varieties  and  remarks  upon.,.   22 

"  Dr.  Higgin's  remarks  on  the  application  thereof  in  mortar  23 
Water-tight  roofs,  on  the  construction  of.   146 


ADDENDA. 


AMERICAN  RESOURCES  OF  MATERIAL,  &c., 

BY  "COSMOrOLlTAN." 

PAGE. 


American  local  resources   166 

Cement  of  the  Romans,  M.  Loriet's  remarks  on  the   174 

Concrete  and  Beton,  strength  of,  and  remarks  on   176 

Experiments,  result  of  the  author's,  ...»   178 


vi.  *  INDEX. 

PAGE. 

Hydraulic  cement,  M.  Pctot's  notes  and  analysis  of.   168 

"                  analysis  of  European   " 

limestone,    "      "   the  Manlius   170 

"            "         "      "    Chittenango   " 

Lime,  mortar,  cement,  concrete,  beton,  &c.,  sundry  opinions  on  175 

Limestone,  United  States  varieties  of.   166 

"       Professor  Roger's  report  of  nagnesian   171 

Ulster  county  hydraulic   „ 

Puzzolana,  analysis  of.   172 

"       trass,  basalt,  and  schistus,  analysis  of.   " 


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